code: func NewTCPListener(listenAddress string, keepAlivePeriod time.Duration) (net.Listener, error) {
  	l, err := net.Listen("tcp", listenAddress)
  	if err != nil {
  		return nil, err
  	}
  	return tcpKeepAliveListener{l.(*net.TCPListener), keepAlivePeriod}, err
  }
docs: // NewTCPListener is Listener specifically for TCP
  //
  // TODO(jeromefroe): Move this into the net package which covers network I/O.