code: func (ch *Channel) writeMsgPacketTo(w io.Writer) (n int, err error) {
  	packet := ch.nextMsgPacket()
  	log.Debug("Write Msg Packet", "conn", ch.conn, "packet", packet)
  	wire.WriteByte(packetTypeMsg, w, &n, &err)
  	wire.WriteBinary(packet, w, &n, &err)
  	if err == nil {
  		ch.recentlySent += int64(n)
  	}
  	return
  }
docs: // Writes next msgPacket to w.
  // Not goroutine-safe