code: func UserAddress() string {
  	//  pam_systemd sets XDG_RUNTIME_DIR but not other dirs.
  	xdgRuntimeDir := os.Getenv("XDG_RUNTIME_DIR")
  	if xdgRuntimeDir != "" {
  		dirs := strings.Split(xdgRuntimeDir, ":")
  		return "unix://" + filepath.Join(dirs[0], "buildkit", "buildkitd.sock")
  	}
  	return Address
  }
docs: // UserAddress typically returns /run/user/$UID/buildkit/buildkitd.sock