}
	if testing.Verbose() {
		fmt.Printf("+ export GOPATH=%s\n", gopath)
		fmt.Printf("+ cd %s\n", modRoot)
	}
	os.Setenv("GOPATH", gopath)
	// Explicitly override GOBIN as well, in case it was set through a GOENV file.
	os.Setenv("GOBIN", filepath.Join(gopath, "bin"))
	os.Chdir(modRoot)
	os.Setenv("PWD", modRoot)

	// The test also needs to install libraries into GOROOT/pkg, so copy the
	// subset of GOROOT that we need.

	)
	runcmd := func(args ...string) ([]byte, error) {
		cmd := exec.Command(args[0], args[1:]...)
		var buf bytes.Buffer
		cmd.Stdout = &buf
		cmd.Stderr = &buf
		cmd.Env = append(os.Environ(), "GOENV=off", "GOFLAGS=")
		if runInDir != "" {
			cmd.Dir = runInDir
			// Set PWD to match Dir to speed up os.Getwd in the child process.
			cmd.Env = append(cmd.Env, "PWD="+cmd.Dir)
		} else {