code: func (uc *UpstreamConfig) String() string {
  	return fmt.Sprintf("%s:%d->%s:%s/%s", uc.LocalBindAddress, uc.LocalBindPort,
  		uc.DestinationType, uc.DestinationNamespace, uc.DestinationName)
  }
docs: // String returns a string that uniquely identifies the Upstream. Used for
  // identifying the upstream in log output and map keys.