inpututil/inpututil.go
func MouseButtonPressDuration(button ebiten.MouseButton) int {
	theInputState.m.RLock()
	s := theInputState.mouseButtonDurations[button]
	theInputState.m.RUnlock()
	return s
}
func MouseButtonPressDuration(button ebiten.MouseButton) int {
	theInputState.m.RLock()
	s := theInputState.mouseButtonDurations[button]
	theInputState.m.RUnlock()
	return s
}
// MouseButtonPressDuration returns how long the mouse button is pressed in frames.
//
// MouseButtonPressDuration is concurrent safe.