code: func Grab(xu *xgbutil.XUtil, win xproto.Window,
  	mods uint16, key xproto.Keycode) {
  
  	for _, m := range xevent.IgnoreMods {
  		xproto.GrabKey(xu.Conn(), true, win, mods|m, key,
  			xproto.GrabModeAsync, xproto.GrabModeAsync)
  	}
  }
docs: // Grab grabs a key with mods on a particular window.
  // This will also grab all combinations of modifiers found in xevent.IgnoreMods.