code: func AddGRPCInfoToMetadata(
  	metadata map[string]string,
  	region string,
  	host, port string,
  	externalHost, externalPort string,
  ) map[string]string {
  	metadata[constants.GRPCHostKey] = host
  	metadata[constants.GRPCPortKey] = port
  	metadata[constants.GRPCExternalHostKey] = externalHost
  	metadata[constants.GRPCExternalPortKey] = externalPort
  	metadata[constants.RegionKey] = region
  	return metadata
  }
docs: // AddGRPCInfoToMetadata adds host, external host and
  // port into metadata