internal/lsp: add the ability to log back to the client

Also use it for errors that were otherwise silently dropped
This makes it much easier to debug problems.

Also added command line control over whether the rpc trace messages are printed, which allows you to read the
log, otherwise the file edit messages swamp the log.

Change-Id: I7b70fd18034a87b2964e6d6d5f6f33dcaf7d8ea8
Reviewed-on: https://go-review.googlesource.com/c/tools/+/170178
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

internal/lsp/cache/check.go

@@ -8,7 +8,6 @@ import (
 	"go/scanner"
 	"go/types"
 	"io/ioutil"
-	"log"
 	"os"
 	"path/filepath"
 	"strings"
@@ -55,7 +54,7 @@ func (v *View) parse(ctx context.Context, f *File) ([]packages.Error, error) {
 		return nil, err
 	}
 	// Add every file in this package to our cache.
-	v.cachePackage(pkg)
+	v.cachePackage(ctx, pkg)
 
 	// If we still have not found the package for the file, something is wrong.
 	if f.pkg == nil {
@@ -64,22 +63,22 @@ func (v *View) parse(ctx context.Context, f *File) ([]packages.Error, error) {
 	return nil, nil
 }
 
-func (v *View) cachePackage(pkg *Package) {
+func (v *View) cachePackage(ctx context.Context, pkg *Package) {
 	for _, file := range pkg.GetSyntax() {
 		// TODO: If a file is in multiple packages, which package do we store?
 		if !file.Pos().IsValid() {
-			log.Printf("invalid position for file %v", file.Name)
+			v.Logger().Errorf(ctx, "invalid position for file %v", file.Name)
 			continue
 		}
 		tok := v.Config.Fset.File(file.Pos())
 		if tok == nil {
-			log.Printf("no token.File for %v", file.Name)
+			v.Logger().Errorf(ctx, "no token.File for %v", file.Name)
 			continue
 		}
 		fURI := span.FileURI(tok.Name())
 		f, err := v.getFile(fURI)
 		if err != nil {
-			log.Printf("no file: %v", err)
+			v.Logger().Errorf(ctx, "no file: %v", err)
 			continue
 		}
 		f.token = tok

internal/lsp/cache/view.go

@@ -13,6 +13,7 @@ import (
 
 	"golang.org/x/tools/go/packages"
 	"golang.org/x/tools/internal/lsp/source"
+	"golang.org/x/tools/internal/lsp/xlog"
 	"golang.org/x/tools/internal/span"
 )
 
@@ -20,6 +21,10 @@ type View struct {
 	// mu protects all mutable state of the view.
 	mu sync.Mutex
 
+	// baseCtx is the context handed to NewView. This is the parent of all
+	// background contexts created for this view.
+	baseCtx context.Context
+
 	// backgroundCtx is the current context used by background tasks initiated
 	// by the view.
 	backgroundCtx context.Context
@@ -28,6 +33,9 @@ type View struct {
 	// should be stopped.
 	cancel context.CancelFunc
 
+	// the logger to use to communicate back with the client
+	log xlog.Logger
+
 	// Name is the user visible name of this view.
 	Name string
 
@@ -80,11 +88,13 @@ type entry struct {
 	ready chan struct{} // closed to broadcast ready condition
 }
 
-func NewView(name string, folder span.URI, config *packages.Config) *View {
+func NewView(ctx context.Context, log xlog.Logger, name string, folder span.URI, config *packages.Config) *View {
-	ctx, cancel := context.WithCancel(context.Background())
+	backgroundCtx, cancel := context.WithCancel(ctx)
 	v := &View{
-		backgroundCtx:  ctx,
+		baseCtx:        ctx,
+		backgroundCtx:  backgroundCtx,
 		cancel:         cancel,
+		log:            log,
 		Config:         *config,
 		Name:           name,
 		Folder:         folder,
@@ -116,11 +126,10 @@ func (v *View) FileSet() *token.FileSet {
 func (v *View) SetContent(ctx context.Context, uri span.URI, content []byte) error {
 	v.mu.Lock()
 	defer v.mu.Unlock()
-
 	// Cancel all still-running previous requests, since they would be
 	// operating on stale data.
 	v.cancel()
-	v.backgroundCtx, v.cancel = context.WithCancel(context.Background())
+	v.backgroundCtx, v.cancel = context.WithCancel(v.baseCtx)
 
 	v.contentChanges[uri] = func() {
 		v.applyContentChange(uri, content)
@@ -277,3 +286,7 @@ func (v *View) mapFile(uri span.URI, f *File) {
 		v.filesByBase[f.basename] = append(v.filesByBase[f.basename], f)
 	}
 }
+
+func (v *View) Logger() xlog.Logger {
+	return v.log
+}

internal/lsp/cmd/cmd.go

@@ -14,6 +14,7 @@ import (
 	"go/ast"
 	"go/parser"
 	"go/token"
+	"log"
 	"net"
 	"os"
 	"strings"
@@ -126,7 +127,7 @@ func (app *Application) connect(ctx context.Context, client protocol.Client) (pr
 		cr, sw, _ := os.Pipe()
 		sr, cw, _ := os.Pipe()
 		var jc *jsonrpc2.Conn
-		jc, server = protocol.NewClient(jsonrpc2.NewHeaderStream(cr, cw), client)
+		jc, server, _ = protocol.NewClient(jsonrpc2.NewHeaderStream(cr, cw), client)
 		go jc.Run(ctx)
 		go lsp.NewServer(jsonrpc2.NewHeaderStream(sr, sw)).Run(ctx)
 	default:
@@ -136,7 +137,7 @@ func (app *Application) connect(ctx context.Context, client protocol.Client) (pr
 		}
 		stream := jsonrpc2.NewHeaderStream(conn, conn)
 		var jc *jsonrpc2.Conn
-		jc, server = protocol.NewClient(stream, client)
+		jc, server, _ = protocol.NewClient(stream, client)
 		if err != nil {
 			return nil, err
 		}
@@ -162,8 +163,22 @@ func (c *baseClient) ShowMessage(ctx context.Context, p *protocol.ShowMessagePar
 func (c *baseClient) ShowMessageRequest(ctx context.Context, p *protocol.ShowMessageRequestParams) (*protocol.MessageActionItem, error) {
 	return nil, nil
 }
-func (c *baseClient) LogMessage(ctx context.Context, p *protocol.LogMessageParams) error { return nil }
+func (c *baseClient) LogMessage(ctx context.Context, p *protocol.LogMessageParams) error {
-func (c *baseClient) Telemetry(ctx context.Context, t interface{}) error                 { return nil }
+	switch p.Type {
+	case protocol.Error:
+		log.Print("Error:", p.Message)
+	case protocol.Warning:
+		log.Print("Warning:", p.Message)
+	case protocol.Info:
+		log.Print("Info:", p.Message)
+	case protocol.Log:
+		log.Print("Log:", p.Message)
+	default:
+		log.Print(p.Message)
+	}
+	return nil
+}
+func (c *baseClient) Telemetry(ctx context.Context, t interface{}) error { return nil }
 func (c *baseClient) RegisterCapability(ctx context.Context, p *protocol.RegistrationParams) error {
 	return nil
 }

internal/lsp/cmd/definition.go

@@ -16,6 +16,7 @@ import (
 	guru "golang.org/x/tools/cmd/guru/serial"
 	"golang.org/x/tools/internal/lsp/cache"
 	"golang.org/x/tools/internal/lsp/source"
+	"golang.org/x/tools/internal/lsp/xlog"
 	"golang.org/x/tools/internal/span"
 	"golang.org/x/tools/internal/tool"
 )
@@ -30,9 +31,9 @@ type Definition struct {
 // help is still valid.
 // They refer to "Set" in "flag.FlagSet" from the DetailedHelp method below.
 const (
-	exampleLine   = 46
+	exampleLine   = 47
 	exampleColumn = 47
-	exampleOffset = 1319
+	exampleOffset = 1359
 )
 
 // definition implements the definition noun for the query command.
@@ -61,7 +62,8 @@ func (d *definition) Run(ctx context.Context, args ...string) error {
 	if len(args) != 1 {
 		return tool.CommandLineErrorf("definition expects 1 argument")
 	}
-	view := cache.NewView("definition_test", span.FileURI(d.query.app.Config.Dir), &d.query.app.Config)
+	log := xlog.New(xlog.StdSink{})
+	view := cache.NewView(ctx, log, "definition_test", span.FileURI(d.query.app.Config.Dir), &d.query.app.Config)
 	from := span.Parse(args[0])
 	f, err := view.GetFile(ctx, from.URI())
 	if err != nil {

internal/lsp/cmd/serve.go

@@ -29,6 +29,7 @@ type Serve struct {
 	Mode    string `flag:"mode" help:"no effect"`
 	Port    int    `flag:"port" help:"port on which to run gopls for debugging purposes"`
 	Address string `flag:"listen" help:"address on which to listen for remote connections"`
+	Trace   bool   `flag:"rpc.trace" help:"Print the full rpc trace in lsp inspector format"`
 
 	app *Application
 }
@@ -71,7 +72,49 @@ func (s *Serve) Run(ctx context.Context, args ...string) error {
 	if s.app.Remote != "" {
 		return s.forward()
 	}
-	logger := func(direction jsonrpc2.Direction, id *jsonrpc2.ID, elapsed time.Duration, method string, payload *json.RawMessage, err *jsonrpc2.Error) {
+
+	// For debugging purposes only.
+	run := func(srv *lsp.Server) {
+		srv.Conn.Logger = logger(s.Trace, out)
+		go srv.Conn.Run(ctx)
+	}
+	if s.Address != "" {
+		return lsp.RunServerOnAddress(ctx, s.Address, run)
+	}
+	if s.Port != 0 {
+		return lsp.RunServerOnPort(ctx, s.Port, run)
+	}
+	stream := jsonrpc2.NewHeaderStream(os.Stdin, os.Stdout)
+	srv := lsp.NewServer(stream)
+	srv.Conn.Logger = logger(s.Trace, out)
+	return srv.Conn.Run(ctx)
+}
+
+func (s *Serve) forward() error {
+	conn, err := net.Dial("tcp", s.app.Remote)
+	if err != nil {
+		return err
+	}
+	errc := make(chan error)
+
+	go func(conn net.Conn) {
+		_, err := io.Copy(conn, os.Stdin)
+		errc <- err
+	}(conn)
+
+	go func(conn net.Conn) {
+		_, err := io.Copy(os.Stdout, conn)
+		errc <- err
+	}(conn)
+
+	return <-errc
+}
+
+func logger(trace bool, out io.Writer) jsonrpc2.Logger {
+	return func(direction jsonrpc2.Direction, id *jsonrpc2.ID, elapsed time.Duration, method string, payload *json.RawMessage, err *jsonrpc2.Error) {
+		if !trace {
+			return
+		}
 		const eol = "\r\n\r\n\r\n"
 		if err != nil {
 			fmt.Fprintf(out, "[Error - %v] %s %s%s %v%s", time.Now().Format("3:04:05 PM"),
@@ -118,39 +161,4 @@ func (s *Serve) Run(ctx context.Context, args ...string) error {
 		fmt.Fprintf(outx, ".\r\nParams: %s%s", params, eol)
 		fmt.Fprintf(out, "%s", outx.String())
 	}
-	// For debugging purposes only.
-	run := func(srv *lsp.Server) {
-		srv.Conn.Logger = logger
-		go srv.Conn.Run(ctx)
-	}
-	if s.Address != "" {
-		return lsp.RunServerOnAddress(ctx, s.Address, run)
-	}
-	if s.Port != 0 {
-		return lsp.RunServerOnPort(ctx, s.Port, run)
-	}
-	stream := jsonrpc2.NewHeaderStream(os.Stdin, os.Stdout)
-	srv := lsp.NewServer(stream)
-	srv.Conn.Logger = logger
-	return srv.Conn.Run(ctx)
-}
-
-func (s *Serve) forward() error {
-	conn, err := net.Dial("tcp", s.app.Remote)
-	if err != nil {
-		return err
-	}
-	errc := make(chan error)
-
-	go func(conn net.Conn) {
-		_, err := io.Copy(conn, os.Stdin)
-		errc <- err
-	}(conn)
-
-	go func(conn net.Conn) {
-		_, err := io.Copy(os.Stdout, conn)
-		errc <- err
-	}(conn)
-
-	return <-errc
 }

internal/lsp/lsp_test.go

@@ -22,6 +22,7 @@ import (
 	"golang.org/x/tools/internal/lsp/cache"
 	"golang.org/x/tools/internal/lsp/protocol"
 	"golang.org/x/tools/internal/lsp/source"
+	"golang.org/x/tools/internal/lsp/xlog"
 	"golang.org/x/tools/internal/span"
 )
 
@@ -34,6 +35,7 @@ func TestLSP(t *testing.T) {
 }
 
 func testLSP(t *testing.T, exporter packagestest.Exporter) {
+	ctx := context.Background()
 	const dir = "testdata"
 
 	// We hardcode the expected number of test cases to ensure that all tests
@@ -70,8 +72,9 @@ func testLSP(t *testing.T, exporter packagestest.Exporter) {
 		return parser.ParseFile(fset, filename, src, parser.AllErrors|parser.ParseComments)
 	}
 
+	log := xlog.New(xlog.StdSink{})
 	s := &Server{
-		view: cache.NewView("lsp_test", span.FileURI(cfg.Dir), &cfg),
+		view: cache.NewView(ctx, log, "lsp_test", span.FileURI(cfg.Dir), &cfg),
 	}
 	// Do a first pass to collect special markers for completion.
 	if err := exported.Expect(map[string]interface{}{

internal/lsp/protocol/client.go

@@ -9,6 +9,7 @@ import (
 	"encoding/json"
 
 	"golang.org/x/tools/internal/jsonrpc2"
+	"golang.org/x/tools/internal/lsp/xlog"
 )
 
 type Client interface {
@@ -24,13 +25,13 @@ type Client interface {
 	PublishDiagnostics(context.Context, *PublishDiagnosticsParams) error
 }
 
-func clientHandler(client Client) jsonrpc2.Handler {
+func clientHandler(log xlog.Logger, client Client) jsonrpc2.Handler {
 	return func(ctx context.Context, conn *jsonrpc2.Conn, r *jsonrpc2.Request) {
 		switch r.Method {
 		case "$/cancelRequest":
 			var params CancelParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			conn.Cancel(params.ID)
@@ -38,51 +39,63 @@ func clientHandler(client Client) jsonrpc2.Handler {
 		case "window/showMessage":
 			var params ShowMessageParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
-			unhandledError(client.ShowMessage(ctx, &params))
+			if err := client.ShowMessage(ctx, &params); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "window/showMessageRequest":
 			var params ShowMessageRequestParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := client.ShowMessageRequest(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "window/logMessage":
 			var params LogMessageParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
-			unhandledError(client.LogMessage(ctx, &params))
+			if err := client.LogMessage(ctx, &params); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "telemetry/event":
 			var params interface{}
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
-			unhandledError(client.Telemetry(ctx, &params))
+			if err := client.Telemetry(ctx, &params); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "client/registerCapability":
 			var params RegistrationParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
-			unhandledError(client.RegisterCapability(ctx, &params))
+			if err := client.RegisterCapability(ctx, &params); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "client/unregisterCapability":
 			var params UnregistrationParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
-			unhandledError(client.UnregisterCapability(ctx, &params))
+			if err := client.UnregisterCapability(ctx, &params); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "workspace/workspaceFolders":
 			if r.Params != nil {
@@ -90,33 +103,41 @@ func clientHandler(client Client) jsonrpc2.Handler {
 				return
 			}
 			resp, err := client.WorkspaceFolders(ctx)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "workspace/configuration":
 			var params ConfigurationParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := client.Configuration(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "workspace/applyEdit":
 			var params ApplyWorkspaceEditParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := client.ApplyEdit(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/publishDiagnostics":
 			var params PublishDiagnosticsParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
-			unhandledError(client.PublishDiagnostics(ctx, &params))
+			if err := client.PublishDiagnostics(ctx, &params); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		default:
 			if r.IsNotify() {

internal/lsp/protocol/log.go

@@ -0,0 +1,32 @@
+package protocol
+
+import (
+	"context"
+
+	"golang.org/x/tools/internal/lsp/xlog"
+)
+
+// logSink implements xlog.Sink in terms of the LogMessage call to a client.
+type logSink struct {
+	client Client
+}
+
+// NewLogger returns an xlog.Sink that sends its messages using client.LogMessage.
+// It maps Debug to the Log level, Info and Error to their matching levels, and
+// does not support warnings.
+func NewLogger(client Client) xlog.Sink {
+	return logSink{client: client}
+}
+
+func (s logSink) Log(ctx context.Context, level xlog.Level, message string) {
+	typ := Log
+	switch level {
+	case xlog.ErrorLevel:
+		typ = Error
+	case xlog.InfoLevel:
+		typ = Info
+	case xlog.DebugLevel:
+		typ = Log
+	}
+	s.client.LogMessage(ctx, &LogMessageParams{Type: typ, Message: message})
+}

internal/lsp/protocol/protocol.go

@@ -6,9 +6,9 @@ package protocol
 
 import (
 	"context"
-	"log"
 
 	"golang.org/x/tools/internal/jsonrpc2"
+	"golang.org/x/tools/internal/lsp/xlog"
 )
 
 const defaultMessageBufferSize = 20
@@ -17,41 +17,32 @@ func canceller(ctx context.Context, conn *jsonrpc2.Conn, req *jsonrpc2.Request)
 	conn.Notify(context.Background(), "$/cancelRequest", &CancelParams{ID: *req.ID})
 }
 
-func NewClient(stream jsonrpc2.Stream, client Client) (*jsonrpc2.Conn, Server) {
+func NewClient(stream jsonrpc2.Stream, client Client) (*jsonrpc2.Conn, Server, xlog.Logger) {
+	log := xlog.New(NewLogger(client))
 	conn := jsonrpc2.NewConn(stream)
 	conn.Capacity = defaultMessageBufferSize
 	conn.RejectIfOverloaded = true
-	conn.Handler = clientHandler(client)
+	conn.Handler = clientHandler(log, client)
 	conn.Canceler = jsonrpc2.Canceler(canceller)
-	return conn, &serverDispatcher{Conn: conn}
+	return conn, &serverDispatcher{Conn: conn}, log
 }
 
-func NewServer(stream jsonrpc2.Stream, server Server) (*jsonrpc2.Conn, Client) {
+func NewServer(stream jsonrpc2.Stream, server Server) (*jsonrpc2.Conn, Client, xlog.Logger) {
 	conn := jsonrpc2.NewConn(stream)
+	client := &clientDispatcher{Conn: conn}
+	log := xlog.New(NewLogger(client))
 	conn.Capacity = defaultMessageBufferSize
 	conn.RejectIfOverloaded = true
-	conn.Handler = serverHandler(server)
+	conn.Handler = serverHandler(log, server)
 	conn.Canceler = jsonrpc2.Canceler(canceller)
-	return conn, &clientDispatcher{Conn: conn}
+	return conn, client, log
 }
 
-func sendParseError(ctx context.Context, conn *jsonrpc2.Conn, req *jsonrpc2.Request, err error) {
+func sendParseError(ctx context.Context, log xlog.Logger, conn *jsonrpc2.Conn, req *jsonrpc2.Request, err error) {
 	if _, ok := err.(*jsonrpc2.Error); !ok {
 		err = jsonrpc2.NewErrorf(jsonrpc2.CodeParseError, "%v", err)
 	}
-	unhandledError(conn.Reply(ctx, req, nil, err))
+	if err := conn.Reply(ctx, req, nil, err); err != nil {
-}
+		log.Errorf(ctx, "%v", err)
-
-// unhandledError is used in places where an error may occur that cannot be handled.
-// This occurs in things like rpc handlers that are a notify, where we cannot
-// reply to the caller, or in a call when we are actually attempting to reply.
-// In these cases, there is nothing we can do with the error except log it, so
-// we do that in this function, and the presence of this function acts as a
-// useful reminder of why we are effectively dropping the error and also a
-// good place to hook in when debugging those kinds of errors.
-func unhandledError(err error) {
-	if err == nil {
-		return
 	}
-	log.Printf("%v", err)
 }

internal/lsp/protocol/server.go

@@ -9,6 +9,7 @@ import (
 	"encoding/json"
 
 	"golang.org/x/tools/internal/jsonrpc2"
+	"golang.org/x/tools/internal/lsp/xlog"
 )
 
 type Server interface {
@@ -51,44 +52,52 @@ type Server interface {
 	FoldingRanges(context.Context, *FoldingRangeParams) ([]FoldingRange, error)
 }
 
-func serverHandler(server Server) jsonrpc2.Handler {
+func serverHandler(log xlog.Logger, server Server) jsonrpc2.Handler {
 	return func(ctx context.Context, conn *jsonrpc2.Conn, r *jsonrpc2.Request) {
 		switch r.Method {
 		case "initialize":
 			var params InitializeParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.Initialize(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "initialized":
 			var params InitializedParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
-			unhandledError(server.Initialized(ctx, &params))
+			if err := server.Initialized(ctx, &params); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "shutdown":
 			if r.Params != nil {
 				conn.Reply(ctx, r, nil, jsonrpc2.NewErrorf(jsonrpc2.CodeInvalidParams, "Expected no params"))
 				return
 			}
-			unhandledError(server.Shutdown(ctx))
+			if err := server.Shutdown(ctx); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "exit":
 			if r.Params != nil {
 				conn.Reply(ctx, r, nil, jsonrpc2.NewErrorf(jsonrpc2.CodeInvalidParams, "Expected no params"))
 				return
 			}
-			unhandledError(server.Exit(ctx))
+			if err := server.Exit(ctx); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "$/cancelRequest":
 			var params CancelParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			conn.Cancel(params.ID)
@@ -96,291 +105,357 @@ func serverHandler(server Server) jsonrpc2.Handler {
 		case "workspace/didChangeWorkspaceFolders":
 			var params DidChangeWorkspaceFoldersParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
-			unhandledError(server.DidChangeWorkspaceFolders(ctx, &params))
+			if err := server.DidChangeWorkspaceFolders(ctx, &params); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "workspace/didChangeConfiguration":
 			var params DidChangeConfigurationParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
-			unhandledError(server.DidChangeConfiguration(ctx, &params))
+			if err := server.DidChangeConfiguration(ctx, &params); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "workspace/didChangeWatchedFiles":
 			var params DidChangeWatchedFilesParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
-			unhandledError(server.DidChangeWatchedFiles(ctx, &params))
+			if err := server.DidChangeWatchedFiles(ctx, &params); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "workspace/symbol":
 			var params WorkspaceSymbolParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.Symbols(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "workspace/executeCommand":
 			var params ExecuteCommandParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.ExecuteCommand(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/didOpen":
 			var params DidOpenTextDocumentParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
-			unhandledError(server.DidOpen(ctx, &params))
+			if err := server.DidOpen(ctx, &params); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/didChange":
 			var params DidChangeTextDocumentParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
-			unhandledError(server.DidChange(ctx, &params))
+			if err := server.DidChange(ctx, &params); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/willSave":
 			var params WillSaveTextDocumentParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
-			unhandledError(server.WillSave(ctx, &params))
+			if err := server.WillSave(ctx, &params); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/willSaveWaitUntil":
 			var params WillSaveTextDocumentParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.WillSaveWaitUntil(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/didSave":
 			var params DidSaveTextDocumentParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
-			unhandledError(server.DidSave(ctx, &params))
+			if err := server.DidSave(ctx, &params); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/didClose":
 			var params DidCloseTextDocumentParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
-			unhandledError(server.DidClose(ctx, &params))
+			if err := server.DidClose(ctx, &params); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/completion":
 			var params CompletionParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.Completion(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "completionItem/resolve":
 			var params CompletionItem
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.CompletionResolve(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/hover":
 			var params TextDocumentPositionParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.Hover(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/signatureHelp":
 			var params TextDocumentPositionParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.SignatureHelp(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/definition":
 			var params TextDocumentPositionParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.Definition(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/typeDefinition":
 			var params TextDocumentPositionParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.TypeDefinition(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/implementation":
 			var params TextDocumentPositionParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.Implementation(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/references":
 			var params ReferenceParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.References(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/documentHighlight":
 			var params TextDocumentPositionParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.DocumentHighlight(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/documentSymbol":
 			var params DocumentSymbolParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.DocumentSymbol(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/codeAction":
 			var params CodeActionParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.CodeAction(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/codeLens":
 			var params CodeLensParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.CodeLens(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "codeLens/resolve":
 			var params CodeLens
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.CodeLensResolve(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/documentLink":
 			var params DocumentLinkParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.DocumentLink(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "documentLink/resolve":
 			var params DocumentLink
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.DocumentLinkResolve(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/documentColor":
 			var params DocumentColorParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.DocumentColor(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/colorPresentation":
 			var params ColorPresentationParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.ColorPresentation(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/formatting":
 			var params DocumentFormattingParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.Formatting(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/rangeFormatting":
 			var params DocumentRangeFormattingParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.RangeFormatting(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/onTypeFormatting":
 			var params DocumentOnTypeFormattingParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.OnTypeFormatting(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/rename":
 			var params RenameParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.Rename(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 
 		case "textDocument/foldingRange":
 			var params FoldingRangeParams
 			if err := json.Unmarshal(*r.Params, &params); err != nil {
-				sendParseError(ctx, conn, r, err)
+				sendParseError(ctx, log, conn, r, err)
 				return
 			}
 			resp, err := server.FoldingRanges(ctx, &params)
-			unhandledError(conn.Reply(ctx, r, resp, err))
+			if err := conn.Reply(ctx, r, resp, err); err != nil {
+				log.Errorf(ctx, "%v", err)
+			}
 		default:
 			if r.IsNotify() {
 				conn.Reply(ctx, r, nil, jsonrpc2.NewErrorf(jsonrpc2.CodeMethodNotFound, "method %q not found", r.Method))

internal/lsp/server.go

@@ -22,6 +22,7 @@ import (
 	"golang.org/x/tools/internal/lsp/cache"
 	"golang.org/x/tools/internal/lsp/protocol"
 	"golang.org/x/tools/internal/lsp/source"
+	"golang.org/x/tools/internal/lsp/xlog"
 	"golang.org/x/tools/internal/span"
 )
 
@@ -29,6 +30,7 @@ import (
 func NewClientServer(client protocol.Client) *Server {
 	return &Server{
 		client: client,
+		log:    xlog.New(protocol.NewLogger(client)),
 	}
 }
 
@@ -36,7 +38,7 @@ func NewClientServer(client protocol.Client) *Server {
 // stream is closed.
 func NewServer(stream jsonrpc2.Stream) *Server {
 	s := &Server{}
-	s.Conn, s.client = protocol.NewServer(stream, s)
+	s.Conn, s.client, s.log = protocol.NewServer(stream, s)
 	return s
 }
 
@@ -68,6 +70,7 @@ func RunServerOnAddress(ctx context.Context, addr string, h func(s *Server)) err
 type Server struct {
 	Conn   *jsonrpc2.Conn
 	client protocol.Client
+	log    xlog.Logger
 
 	initializedMu sync.Mutex
 	initialized   bool // set once the server has received "initialize" request
@@ -117,8 +120,11 @@ func (s *Server) Initialize(ctx context.Context, params *protocol.InitializePara
 	// flag). Disabled for now to simplify debugging.
 	s.textDocumentSyncKind = protocol.Full
 
+	//We need a "detached" context so it does not get timeout cancelled.
+	//TODO(iancottrell): Do we need to copy any values across?
+	viewContext := context.Background()
 	//TODO:use workspace folders
-	s.view = cache.NewView(path.Base(string(rootURI)), rootURI, &packages.Config{
+	s.view = cache.NewView(viewContext, s.log, path.Base(string(rootURI)), rootURI, &packages.Config{
 		Context: ctx,
 		Dir:     rootPath,
 		Env:     os.Environ(),
@@ -566,13 +572,6 @@ func (s *Server) FoldingRanges(context.Context, *protocol.FoldingRangeParams) ([
 	return nil, notImplemented("FoldingRanges")
 }
 
-func (s *Server) Error(err error) {
-	s.client.LogMessage(context.Background(), &protocol.LogMessageParams{
-		Type:    protocol.Error,
-		Message: fmt.Sprint(err),
-	})
-}
-
 func (s *Server) processConfig(config interface{}) error {
 	//TODO: we should probably store and process more of the config
 	c, ok := config.(map[string]interface{})

internal/lsp/source/diagnostics.go

@@ -8,7 +8,6 @@ import (
 	"bytes"
 	"context"
 	"fmt"
-	"log"
 
 	"golang.org/x/tools/go/analysis"
 	"golang.org/x/tools/go/analysis/passes/asmdecl"
@@ -90,7 +89,8 @@ func Diagnostics(ctx context.Context, v View, uri span.URI) (map[span.URI][]Diag
 			if diagFile, err := v.GetFile(ctx, spn.URI()); err == nil {
 				tok := diagFile.GetToken(ctx)
 				if tok == nil {
-					continue // ignore errors
+					v.Logger().Errorf(ctx, "Could not matching tokens for diagnostic: %v", diagFile.URI())
+					continue
 				}
 				content := diagFile.GetContent(ctx)
 				c := span.NewTokenConverter(diagFile.GetFileSet(ctx), tok)
@@ -124,7 +124,7 @@ func Diagnostics(ctx context.Context, v View, uri span.URI) (map[span.URI][]Diag
 		if err != nil {
 			//TODO: we could not process the diag.Pos, and thus have no valid span
 			//we don't have anywhere to put this error though
-			log.Print(err)
+			v.Logger().Errorf(ctx, "%v", err)
 		}
 		category := a.Name
 		if diag.Category != "" {

internal/lsp/source/view.go

@@ -12,6 +12,7 @@ import (
 
 	"golang.org/x/tools/go/analysis"
 	"golang.org/x/tools/go/packages"
+	"golang.org/x/tools/internal/lsp/xlog"
 	"golang.org/x/tools/internal/span"
 )
 
@@ -19,6 +20,7 @@ import (
 // package. The view provides access to files and their contents, so the source
 // package does not directly access the file system.
 type View interface {
+	Logger() xlog.Logger
 	GetFile(ctx context.Context, uri span.URI) (File, error)
 	SetContent(ctx context.Context, uri span.URI, content []byte) error
 	FileSet() *token.FileSet

internal/lsp/xlog/xlog.go

@@ -0,0 +1,71 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xlog
+
+import (
+	"context"
+	"fmt"
+	"log"
+)
+
+// Logger is a wrapper over a sink to provide a clean API over the core log
+// function.
+type Logger struct {
+	sink Sink
+}
+
+// Level indicates the severity of the logging message.
+type Level int
+
+const (
+	ErrorLevel = Level(iota)
+	InfoLevel
+	DebugLevel
+)
+
+// Sink is the interface to something that consumes logging messages.
+// This can be implemented and then registered with a context to control the
+// destination or formatting of logging.
+type Sink interface {
+	Log(ctx context.Context, level Level, message string)
+}
+
+// StdSink is a Sink that writes to the standard log package.
+type StdSink struct{}
+
+// New returns a logger for the provided sink.
+func New(sink Sink) Logger {
+	return Logger{sink: sink}
+}
+
+// Errorf is intended for the logging of errors that we could not easily return
+// to the client but that caused problems internally.
+func (l Logger) Errorf(ctx context.Context, format string, args ...interface{}) {
+	l.sink.Log(ctx, ErrorLevel, fmt.Sprintf(format, args...))
+}
+
+// Infof is intended for logging of messages that may help the user understand
+// the behavior or be useful in a bug report.
+func (l Logger) Infof(ctx context.Context, format string, args ...interface{}) {
+	l.sink.Log(ctx, InfoLevel, fmt.Sprintf(format, args...))
+}
+
+// Debugf is intended to be used only while debugging.
+func (l Logger) Debugf(ctx context.Context, format string, args ...interface{}) {
+	l.sink.Log(ctx, DebugLevel, fmt.Sprintf(format, args...))
+}
+
+// Log implements Sink for the StdSink.
+// It writes the message using log.Print with a level based prefix.
+func (StdSink) Log(ctx context.Context, level Level, message string) {
+	switch level {
+	case ErrorLevel:
+		log.Print("Error: ", message)
+	case InfoLevel:
+		log.Print("Info: ", message)
+	case DebugLevel:
+		log.Print("Debug: ", message)
+	}
+}