code: func Ungrab(xu *xgbutil.XUtil, win xproto.Window, mods uint16,
  	button xproto.Button) {
  
  	for _, m := range xevent.IgnoreMods {
  		xproto.UngrabButtonChecked(xu.Conn(), byte(button), win, mods|m).Check()
  	}
  }
docs: // Ungrab undoes Grab. It will handle all combinations of modifiers found
  // in xevent.IgnoreMods.