code: func NetAddressKey(na *wire.NetAddress) string {
  	port := strconv.FormatUint(uint64(na.Port), 10)
  
  	return net.JoinHostPort(ipString(na), port)
  }
docs: // NetAddressKey returns a string key in the form of ip:port for IPv4 addresses
  // or [ip]:port for IPv6 addresses.