playfab_test.cs

using Godot;
using System;
using System.Runtime;
using System.Threading;
using System.Threading.Tasks;
using PlayFab;
using PlayFab.ClientModels;

public class Main : Node
{
    private static bool _running = true;
    public override void _Ready()
    {
        PlayFabSettings.TitleId = "258B"; // Please change this value to your own titleId from PlayFab Game Manager
        var request = new LoginWithCustomIDRequest{ CustomId = "GettingStartedGuide", CreateAccount = true };
        var loginTask = PlayFabClientAPI.LoginWithCustomIDAsync(request);
        // If you want a synchronous ressult, you can call loginTask.Wait() - Note, this will halt the program until the function returns

        while (_running)
        {
            if (loginTask.IsCompleted) // You would probably want a more sophisticated way of tracking pending async API calls in a real game
            {
                OnLoginComplete(loginTask);
            }

            // Presumably this would be your main game loop, doing other things
            // System.Threading.Thread.Sleep(1);
        }

        GD.Print("Done! Press any key to close");
    }

    private static void OnLoginComplete(Task<PlayFabResult<LoginResult>> taskResult)
    {
        var apiError = taskResult.Result.Error;
        var apiResult = taskResult.Result.Result;

        if (apiError != null)
        {
            GD.Print("Something went wrong with your first API call.  :(");
            GD.Print("Here's some debug information:");
            GD.Print(PlayFabUtil.GenerateErrorReport(apiError));
        }
        else if (apiResult != null)
        {
            GD.Print("Congratulations, you made your first successful API call!");
        }

        _running = false; // Because this is just an example, successful login triggers the end of the program
    }
}