將以下程式碼加入AppDelegate內

gistfile1.txt

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
        
        var error : NSError?
        GGLContext.sharedInstance().configureWithError(&error)
        
        if error != nil{
            print(error)
        }
        
        return true
    }
    
    
    //按下登入鈕後，畫面會跳轉到網頁，進行帳號密碼確認，此方法實作確認完帳號密碼後，畫面跳轉回原ViewController
    func application(_ app: UIApplication, open url: URL, options: [UIApplicationOpenURLOptionsKey : Any] = [:]) -> Bool {
        
        return GIDSignIn.sharedInstance().handle(url, sourceApplication: options[UIApplicationOpenURLOptionsKey.sourceApplication] as? String, annotation: options[UIApplicationOpenURLOptionsKey.annotation])
    }