这里的缓动变黑可以用DOTWeen的  DOTween.To

private CanvasGroup fadeCanvaseGroup;
private bool isFade; 

private void Start() 
{ 
  fadeCanvaseGroup = FindObjectOfType();
  Fade(1); 
} 
private void Fade(float alpha) 
{
  isFade = true; DOTween.To(() => fadeCanvaseGroup.alpha, a => fadeCanvaseGroup.alpha = a, alpha, 10);
}

定时销毁可以不用协程

Destroy(gameObject, timer);

timer就是时间

放在Start即可