code: func WmSyncRequestCounter(xu *xgbutil.XUtil, win xproto.Window) (uint, error) {
  	return xprop.PropValNum(xprop.GetProperty(xu, win,
  		"_NET_WM_SYNC_REQUEST_COUNTER"))
  }
docs: // _NET_WM_SYNC_REQUEST_COUNTER get
  // I'm pretty sure this needs 64 bit integers, but I'm not quite sure
  // how to go about that yet. Any ideas?