code: func NewUpstreamListener(svc *connect.Service, client *api.Client,
  	cfg UpstreamConfig, logger *log.Logger) *Listener {
  	return newUpstreamListenerWithResolver(svc, cfg,
  		UpstreamResolverFuncFromClient(client), logger)
  }
docs: // NewUpstreamListener returns a Listener setup to listen locally for TCP
  // connections that are proxied to a discovered Connect service instance.