How to get GooglePlayGames Current user's id?

Hear is my code;

void Start () {
	PlayGamesPlatform.Activate();
	GooglePlayLOGIN();
	DontDestroyOnLoad(this.gameObject);
}

void OnGUI()
{
	GUI.Label(new Rect (Screen.width*0.5f,Screen.height*0.5f,1000,30),"11"+GooglePlayGodinID);
}

void GooglePlayLOGIN()
{
	Social.localUser.Authenticate((bool success) =>
	  {
	     if(success)
		{
			GooglePlayGodinID=PlayGamesPlatform.Instance.GetUserId();
		}else{

		}
	});
}

How to get Current User’s Id? This code returns NULL Help me pls

PlayGamesPlatform.Instance.localUser.id
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