code: func NewKCP(conv uint32, output output_callback) *KCP {
  	kcp := new(KCP)
  	kcp.conv = conv
  	kcp.snd_wnd = IKCP_WND_SND
  	kcp.rcv_wnd = IKCP_WND_RCV
  	kcp.rmt_wnd = IKCP_WND_RCV
  	kcp.mtu = IKCP_MTU_DEF
  	kcp.mss = kcp.mtu - IKCP_OVERHEAD
  	kcp.buffer = make([]byte, kcp.mtu)
  	kcp.rx_rto = IKCP_RTO_DEF
  	kcp.rx_minrto = IKCP_RTO_MIN
  	kcp.interval = IKCP_INTERVAL
  	kcp.ts_flush = IKCP_INTERVAL
  	kcp.ssthresh = IKCP_THRESH_INIT
  	kcp.dead_link = IKCP_DEADLINK
  	kcp.output = output
  	return kcp
  }
docs: // NewKCP create a new kcp control object, 'conv' must equal in two endpoint
  // from the same connection.