all: GOSUMDB=off for tests that use fake modules

Users of packagestest will create modules that don't exist on the
Internet and can change. There's no point in checking sum.golang.org for
them under any circumstances.

Similarly for the various goimports tests.

Fixes golang/go#32216.

Change-Id: Id9a6b660564cb744530bf9d209fca19008fb9c4f
Reviewed-on: https://go-review.googlesource.com/c/tools/+/178722
Reviewed-by: Ian Cottrell <iancottrell@google.com>

go/packages/packagestest/modules.go

@@ -116,7 +116,9 @@ func (modules) Finalize(exported *Exported) error {
 	exported.Config.Env = append(exported.Config.Env,
 		"GO111MODULE=on",
 		"GOPATH="+filepath.Join(exported.temp, "modcache"),
-		"GOPROXY="+proxyDirToURL(proxyDir))
+		"GOPROXY="+proxyDirToURL(proxyDir),
+		"GOSUMDB=off",
+	)
 
 	// Run go mod download to recreate the mod cache dir with all the extra
 	// stuff in cache. All the files created by Export should be recreated.

internal/imports/fix.go

@@ -506,8 +506,8 @@ type ProcessEnv struct {
 
 	// If non-empty, these will be used instead of the
 	// process-wide values.
-	GOPATH, GOROOT, GO111MODULE, GOPROXY, GOFLAGS string
-	WorkingDir                                    string
+	GOPATH, GOROOT, GO111MODULE, GOPROXY, GOFLAGS, GOSUMDB string
+	WorkingDir                                             string
 
 	// If true, use go/packages regardless of the environment.
 	ForceGoPackages bool
@@ -527,6 +527,7 @@ func (e *ProcessEnv) env() []string {
 	add("GO111MODULE", e.GO111MODULE)
 	add("GOPROXY", e.GOPROXY)
 	add("GOFLAGS", e.GOFLAGS)
+	add("GOSUMDB", e.GOSUMDB)
 	if e.WorkingDir != "" {
 		add("PWD", e.WorkingDir)
 	}

internal/imports/fix_test.go

@@ -1572,6 +1572,7 @@ func (c testConfig) test(t *testing.T, fn func(*goimportTest)) {
 					GOROOT:          env["GOROOT"],
 					GOPATH:          env["GOPATH"],
 					GO111MODULE:     env["GO111MODULE"],
+					GOSUMDB:         env["GOSUMDB"],
 					WorkingDir:      exported.Config.Dir,
 					ForceGoPackages: forceGoPackages,
 					Debug:           *testDebug,

internal/imports/mod_test.go

@@ -520,6 +520,7 @@ func setup(t *testing.T, main, wd string) *modTest {
 		GOPATH:      filepath.Join(dir, "gopath"),
 		GO111MODULE: "on",
 		GOPROXY:     proxyDirToURL(proxyDir),
+		GOSUMDB:     "off",
 		WorkingDir:  filepath.Join(mainDir, wd),
 	}