创建App-Google sign in my App

创建App-Google sign in my App

本App设想登入方法有Google、AppleID、FB等三种方法来登入，现在来使用以下编码达成使用Google登入吧！
编码:

 [GIDSignIn.sharedInstance
    signInWithConfiguration:signInConfig
   presentingViewController:self
                   callback:^(GIDGoogleUser * _Nullable user,
                              NSError * _Nullable error) {
      if (error) { return; }
      if (user == nil) { return; }

    // Your user is signed in!
}]; 

将***按钮***连接到signInWithConfiguration:presentingViewController:callback: