ClientInterceptor and Firebase IdToken

[developerGM]

Hi, I am rad your article and I think that is really interesting.
But I would like to know how can I solve a problem...I need to ask to sdk Firebase the token

Hi, I am trying to extends ClientInterceptor to append some headers and ask to Firebase to give me a IdToken but I don't understand how can do it because task.getResult() go to in exception java.lang.IllegalStateException: Task is not yet complete

I have tried also with a sync mode
GetTokenResult tokenResult = Tasks.await(task, 20, TimeUnit.SECONDS);
but nothing, exception main thread

public class CustomHeaderInterceptor implements ClientInterceptor {
    @Override
    public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(MethodDescriptor<ReqT, RespT> method, CallOptions callOptions, Channel next) {
        return new ForwardingClientCall.SimpleForwardingClientCall<ReqT, RespT>(next.newCall(method, callOptions)) {
            @Override
            public void start(Listener<RespT> responseListener, Metadata headers) {
                headers.put(Metadata.Key.of("X-XXX", Metadata.ASCII_STRING_MARSHALLER), "test_test");

                try {
                    FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
                    if (user == null) {
                        throw new Exception("User is not logged in.");
                    } else {
                        Task<GetTokenResult> task = user.getIdToken(false);
                        GetTokenResult tokenResult = task.getResult();

                        String idToken = tokenResult.getToken();
                        headers.put(Metadata.Key.of("Authorization", Metadata.ASCII_STRING_MARSHALLER), "Bearer " + idToken);

                        super.start(responseListener, headers);
                    }
                } catch (Exception e) {
                    Log.d(this.getClass().getName(), new Gson().toJson(e));
                }
            }
        };
    }
}

How can you solve this problem?