title: How to get access token in firebase login with provider
body: <p>I'm setting up login on my app with firebase, i'm choose Github provider for my login provider. I try to debug and access data from debug variable but can't access from code. here my code:</p>
  
  <pre><code>var firebaseAuth = FirebaseAuth.getInstance()
  var provider: OAuthProvider.Builder = OAuthProvider.newBuilder("github.com")
  
  // login handler
          btn_login.setOnClickListener {
              firebaseAuth.startActivityForSignInWithProvider(this, provider.build())
                  .addOnSuccessListener{ result: AuthResult -&gt;
                      System.out.println(result.credential)
                  }
                  .addOnFailureListener {
                          exception -&gt; print(exception)
                  }
          }
  </code></pre>
  
  <p>and System.out:</p>
  
  <pre><code>I/System.out: com.google.firebase.auth.FirebaseAuthWebException: The web operation was canceled by the user.com.google.firebase.auth.zzg@588c9c4
  </code></pre>
  
  <p>From debug I found where the access token is, but I can't access it.</p>
  
  <pre><code>((result as zzh).zzc as zzg).accessToken
  //399kdkkda0XXXXX
  </code></pre>
  
  <p>Thank you for your help</p>