6 files changed, 50 insertions, 0 deletions
diff --git a/src/cmd/go/alldocs.go b/src/cmd/go/alldocs.go
index fd95da23eb..90eb3e2a00 100644
--- a/src/cmd/go/alldocs.go
+++ b/src/cmd/go/alldocs.go
@@ -1903,6 +1903,12 @@
 // 	GCCGOTOOLDIR
 // 		If set, where to find gccgo tools, such as cgo.
 // 		The default is based on how gccgo was configured.
+// 	GOEXPERIMENT
+// 		Comma-separated list of toolchain experiments to enable or disable.
+// 		The list of available experiments may change arbitrarily over time.
+// 		See src/internal/goexperiment/flags.go for currently valid values.
+// 		Warning: This variable is provided for the development and testing
+// 		of the Go toolchain itself. Use beyond that purpose is unsupported.
 // 	GOROOT_FINAL
 // 		The root of the installed Go tree, when it is
 // 		installed in a location other than where it is built.
diff --git a/src/cmd/go/internal/envcmd/env.go b/src/cmd/go/internal/envcmd/env.go
index d88dcce5c0..1553d26391 100644
--- a/src/cmd/go/internal/envcmd/env.go
+++ b/src/cmd/go/internal/envcmd/env.go
@@ -73,6 +73,7 @@ func MkEnv() []cfg.EnvVar {
 		{Name: "GOCACHE", Value: cache.DefaultDir()},
 		{Name: "GOENV", Value: envFile},
 		{Name: "GOEXE", Value: cfg.ExeSuffix},
+		{Name: "GOEXPERIMENT", Value: buildcfg.GOEXPERIMENT()},
 		{Name: "GOFLAGS", Value: cfg.Getenv("GOFLAGS")},
 		{Name: "GOHOSTARCH", Value: runtime.GOARCH},
 		{Name: "GOHOSTOS", Value: runtime.GOOS},
@@ -364,6 +365,13 @@ func checkBuildConfig(add map[string]string, del map[string]bool) error {
 		}
 	}
 
+	goexperiment, okGOEXPERIMENT := get("GOEXPERIMENT", buildcfg.GOEXPERIMENT(), "")
+	if okGOEXPERIMENT {
+		if _, _, err := buildcfg.ParseGOEXPERIMENT(goos, goarch, goexperiment); err != nil {
+			return err
+		}
+	}
+
 	return nil
 }
 
diff --git a/src/cmd/go/internal/help/helpdoc.go b/src/cmd/go/internal/help/helpdoc.go
index b552777e3e..490ff1fb7c 100644
--- a/src/cmd/go/internal/help/helpdoc.go
+++ b/src/cmd/go/internal/help/helpdoc.go
@@ -610,6 +610,12 @@ Special-purpose environment variables:
 	GCCGOTOOLDIR
 		If set, where to find gccgo tools, such as cgo.
 		The default is based on how gccgo was configured.
+	GOEXPERIMENT
+		Comma-separated list of toolchain experiments to enable or disable.
+		The list of available experiments may change arbitrarily over time.
+		See src/internal/goexperiment/flags.go for currently valid values.
+		Warning: This variable is provided for the development and testing
+		of the Go toolchain itself. Use beyond that purpose is unsupported.
 	GOROOT_FINAL
 		The root of the installed Go tree, when it is
 		installed in a location other than where it is built.
diff --git a/src/cmd/go/testdata/script/env_exp.txt b/src/cmd/go/testdata/script/env_exp.txt
new file mode 100644
index 0000000000..681512d87c
--- /dev/null
+++ b/src/cmd/go/testdata/script/env_exp.txt
@@ -0,0 +1,17 @@
+# Test GOEXPERIMENT variable
+
+# go env shows default empty GOEXPERIMENT
+go env
+stdout GOEXPERIMENT=
+
+# go env shows valid experiments
+env GOEXPERIMENT=fieldtrack,staticlockranking
+go env GOEXPERIMENT
+stdout '.*fieldtrack.*staticlockranking.*'
+go env
+stdout 'GOEXPERIMENT=.*fieldtrack.*staticlockranking.*'
+
+# go env rejects unknown experiments
+env GOEXPERIMENT=bad
+! go env GOEXPERIMENT
+stderr 'unknown GOEXPERIMENT bad'
diff --git a/src/cmd/go/testdata/script/env_unset.txt b/src/cmd/go/testdata/script/env_unset.txt
index 35fbb0a8a2..4e0f249509 100644
--- a/src/cmd/go/testdata/script/env_unset.txt
+++ b/src/cmd/go/testdata/script/env_unset.txt
@@ -4,6 +4,12 @@
 env GOENV=badenv
 env GOOS=
 env GOARCH=
+env GOEXPERIMENT=
+
+! go env
+stderr '^go(\.exe)?: unknown GOEXPERIMENT badexp$'
+
+go env -u GOEXPERIMENT
 
 ! go env
 stderr '^cmd/go: unsupported GOOS/GOARCH pair bados/badarch$'
@@ -21,3 +27,4 @@ go env
 -- badenv --
 GOOS=bados
 GOARCH=badarch
+GOEXPERIMENT=badexp
diff --git a/src/cmd/go/testdata/script/env_write.txt b/src/cmd/go/testdata/script/env_write.txt
index 4fa39df104..b5e9739167 100644
--- a/src/cmd/go/testdata/script/env_write.txt
+++ b/src/cmd/go/testdata/script/env_write.txt
@@ -179,3 +179,9 @@ stderr 'unsupported GOOS/GOARCH.*windows/mips$'
 stderr 'go env -w: GOMODCACHE entry is relative; must be absolute path: "~/test"'
 ! go env -w GOMODCACHE=./test
 stderr 'go env -w: GOMODCACHE entry is relative; must be absolute path: "./test"'
+
+# go env -w checks validity of GOEXPERIMENT
+env GOEXPERIMENT=
+! go env -w GOEXPERIMENT=badexp
+stderr 'unknown GOEXPERIMENT badexp'
+go env -w GOEXPERIMENT=fieldtrack