stderr 'go: downloading go1.20 '


# check for invalid GOTOOLCHAIN
env GOTOOLCHAIN=go1.14
go version
stdout 'go1.14'

env GOTOOLCHAIN=go1.20
! go version
stderr 'go: downloading go1.20 '

env GOTOOLCHAIN=go1.21
! go version
stderr 'go: invalid toolchain: go1.21 is a language version but not a toolchain version \(go1.21.x\)'

env GOTOOLCHAIN=go1.22
! go version

env GOTOOLCHAIN=go1.600
go version
stdout go1.600

env GOTOOLCHAIN=go1.400
go version
stdout go1.400

# GOTOOLCHAIN=version+auto sets a minimum.
env GOTOOLCHAIN=go1.600+auto
go version
stdout go1.600

env GOTOOLCHAIN=go1.400.0+auto
go version
stdout go1.400.0

# GOTOOLCHAIN=version+path sets a minimum too.
env GOTOOLCHAIN=go1.600+path
go version
stdout go1.600

env GOTOOLCHAIN=go1.400+path

# GOTOOLCHAIN from network
[!exec:/bin/sh] stop 'the fake proxy serves shell scripts instead of binaries'
env GOTOOLCHAIN=go1.999testmod
go version
stderr 'go: downloading go1.999testmod \(.*/.*\)'

# GOTOOLCHAIN cached from network
go version
! stderr downloading
stdout go1.999testmod

# GOTOOLCHAIN with GOSUMDB enabled but at a bad URL should operate in cache and not try badurl
env oldsumdb=$GOSUMDB

		return
	}

	// Interpret GOTOOLCHAIN to select the Go toolchain to run.
	gotoolchain := cfg.Getenv("GOTOOLCHAIN")
	gover.Startup.GOTOOLCHAIN = gotoolchain
	if gotoolchain == "" {
		// cfg.Getenv should fall back to $GOROOT/go.env,
		// so this should not happen, unless a packager
		// has deleted the GOTOOLCHAIN line from go.env.
		// It can also happen if GOROOT is missing or broken,

# Test query for non-defaults in the env

env GOROOT=./a
env GOTOOLCHAIN=local
env GOSUMDB=nodefault
env GOPROXY=nodefault
env GO111MODULE=auto
env CGO_CFLAGS=nodefault
env CGO_CPPFLAGS=nodefault

go env -changed
# linux output like GOTOOLCHAIN='local'
# windows output like GOTOOLCHAIN=local
stdout 'GOTOOLCHAIN=''?local''?'
stdout 'GOSUMDB=''?nodefault''?'
stdout 'GOPROXY=''?nodefault''?'
stdout 'GO111MODULE=''?auto''?'

stdout go1.21pre3

# GOTOOLCHAIN=go1.50.0
env GOTOOLCHAIN=go1.50.0
! go version
stderr 'running go1.50.0 from PATH'

# GOTOOLCHAIN=path with toolchain line
env GOTOOLCHAIN=local
go mod init m
go mod edit -toolchain=go1.50.0
grep go1.50.0 go.mod
env GOTOOLCHAIN=path
! go version
stderr 'running go1.50.0 from PATH'

# GOTOOLCHAIN=path with go line
env GOTOOLCHAIN=local
go mod edit -toolchain=none -go=1.50.0

# a module zip that we don't understand.

# GOTOOLCHAIN=auto should run the newer toolchain
env GOTOOLCHAIN=auto
go mod download rsc.io/needgo121@latest rsc.io/needgo122@latest rsc.io/needgo123@latest rsc.io/needall@latest
stderr '^go: rsc.io/needall@v0.0.1 requires go >= 1.23; switching to go1.23.9$'
! stderr '\(running'

# GOTOOLCHAIN=min+auto should run the newer toolchain
env GOTOOLCHAIN=go1.21+auto

	"runtime"
	"syscall"
)

// execGoToolchain execs the Go toolchain with the given name (gotoolchain),
// GOROOT directory, and go command executable.
// The GOROOT directory is empty if we are invoking a command named
// gotoolchain found in $PATH.
func execGoToolchain(gotoolchain, dir, exe string) {
	os.Setenv(targetEnv, gotoolchain)
	if dir == "" {
		os.Unsetenv("GOROOT")
	} else {
		os.Setenv("GOROOT", dir)
	}

	GoVersion string
	Toolchain string // for callers if they want to use it, but not printed
}

func (e *TooNewError) Error() string {
	var explain string
	if Startup.GOTOOLCHAIN != "" && Startup.GOTOOLCHAIN != "auto" {
		explain = "; GOTOOLCHAIN=" + Startup.GOTOOLCHAIN
	}
	if Startup.AutoFile != "" && (Startup.AutoGoVersion != "" || Startup.AutoToolchain != "") {
		explain += fmt.Sprintf("; %s sets ", base.ShortPath(Startup.AutoFile))

	}
	return "go" + latest, nil
}

// HasAuto reports whether the GOTOOLCHAIN setting allows "auto" upgrades.
func HasAuto() bool {
	env := cfg.Getenv("GOTOOLCHAIN")
	return env == "auto" || strings.HasSuffix(env, "+auto")
}

// HasPath reports whether the GOTOOLCHAIN setting allows "path" upgrades.
func HasPath() bool {
	env := cfg.Getenv("GOTOOLCHAIN")
	return env == "path" || strings.HasSuffix(env, "+path")