code: func getCachedInfo(c context.Context) (*signing.ServiceInfo, error) {
  	v, err := infoCache.Fetch(c, func(interface{}) (interface{}, time.Duration, error) {
  		account, err := info.ServiceAccount(c)
  		if err != nil {
  			return nil, 0, err
  		}
  		return &signing.ServiceInfo{
  			AppID:              info.AppID(c),
  			AppRuntime:         "go",
  			AppRuntimeVersion:  runtime.Version(),
  			AppVersion:         strings.Split(info.VersionID(c), ".")[0],
  			ServiceAccountName: account,
  		}, 0, nil
  	})
  	if err != nil {
  		return nil, err
  	}
  	return v.(*signing.ServiceInfo), nil
  }
docs: // getCachedINfo caches this app service info in local memory forever.
  //
  // This info is static during lifetime of the process.