code: func GetRuntimeDir() (string, error) {
  	if xdgRuntimeDir := os.Getenv("XDG_RUNTIME_DIR"); xdgRuntimeDir != "" {
  		return xdgRuntimeDir, nil
  	}
  	return "", errors.New("could not get XDG_RUNTIME_DIR")
  }
docs: // GetRuntimeDir returns XDG_RUNTIME_DIR.
  // XDG_RUNTIME_DIR is typically configured via pam_systemd.
  // GetRuntimeDir returns non-nil error if XDG_RUNTIME_DIR is not set.
  //
  // See also https://standards.freedesktop.org/basedir-spec/latest/ar01s03.html