Google Play Service SignIn script in Unity3d using Google Play services Unity plugin

GooglePlayServices.cs

/*
 *	GooglePlayServices.cs (c) by Nipun David
 *
 *	GooglePlayServices.cs is licensed under a
 *	Creative Commons Attribution-ShareAlike 4.0 International License.
 *
 *	You should have received a copy of the license along with this
 *	work. If not, see <http://creativecommons.org/licenses/by-sa/4.0/>.
 */

using UnityEngine;
using System.Collections;
using GooglePlayGames;
using UnityEngine.SocialPlatforms;

public class GooglePlayServices : MonoBehaviour {

	// Use this for initialization
	void Start () {
		// Code to initialize this object would go here

		// for debug verbose
		PlayGamesPlatform.DebugLogEnabled = true;
		// initialize the google play services
		PlayGamesPlatform.Activate ();
		TrySilentSignIn ();
	}
	
	// Update is called once per frame
	void Update () {
	
	}

	public void TrySilentSignIn() {
		if (! PlayGamesPlatform.Instance.localUser.authenticated) {
			PlayGamesPlatform.Instance.Authenticate ((bool success) => {
				if (success) {
					Debug.Log ("GPS - GPS - Silently signed in! Welcome " + PlayGamesPlatform.Instance.localUser.userName);
				} else {
					Debug.Log ("GPS - Oh... we're not signed in.");
				}
			}, true);
		} else {
			Debug.Log("GPS - We're already signed in");
		}
	}

	public void SignInAndStart() {
		if (!IsAuthenticated()) {
			PlayGamesPlatform.Instance.localUser.Authenticate((bool success) => {
				if (success) {
					Debug.Log ("GPS - We're signed in! Welcome " + PlayGamesPlatform.Instance.localUser.userName);
					// We could start our game now
				} else {
					Debug.Log ("GPS - Oh... we're not signed in.");
				}
			});
		} else {
			Debug.Log ("GPS - You're already signed in.");
			// We could also start our game now
			// Actually Multiplayer game begins
		}
	}

	public bool IsAuthenticated() {
		return PlayGamesPlatform.Instance.localUser.authenticated;
	}


	public void SignOut() {
		PlayGamesPlatform.Instance.SignOut ();
	}

	public void pushScore(int score) {
		// post score 12345 to leaderboard ID "Cfji293fjsie_QA")
		if (IsAuthenticated ()) {
			Social.ReportScore (score, GameIDs.leaderboard_score, (bool success) => {
				// handle success or failure
				if (success) {
					Debug.Log ("Score Pushed");
				} else {
					Debug.Log ("Score Not Pushed");
				}
			});
		}
	}

	public void showLeaderboard() {
		if (IsAuthenticated()) {
			Social.ShowLeaderboardUI ();
		} else {
			SignInAndStart ();
		}
	}
}