code: func (w *Window) Monitor() *Monitor {
  	var monitor *glfw.Monitor
  	mainthread.Call(func() {
  		monitor = w.window.GetMonitor()
  	})
  	if monitor == nil {
  		return nil
  	}
  	return &Monitor{
  		monitor: monitor,
  	}
  }
docs: // Monitor returns a monitor the Window is fullscreen on. If the Window is not fullscreen, this
  // function returns nil.