GameLoopExample.cs

namespace ConsoleApp;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.VisualStudio.Threading;

class Program {


    private static async Task Main(string[] args) {
        var game = new Game();
        new Timer( i => game.ActionAsync().Wait(), null, 0, 3000 );
        game.Run();
    }


}

public class Game {

    private GameTaskScheduler TaskScheduler { get; } = new GameTaskScheduler();


    public Game() {
    }


    // Run game loop
    public void Run() {
        while (true) {
            TaskScheduler.Execute();

            // Game logic
            Console.WriteLine( "Update: {0:00}", Environment.CurrentManagedThreadId );
            Thread.Sleep( 1000 );
        }
    }


    // User action
    public async Task ActionAsync() {
        await SwitchToMainThread(); // Switch to game thread
        Console.WriteLine( "Action: {0:00}", Environment.CurrentManagedThreadId );
    }


    // Utils
    public AwaitExtensions.TaskSchedulerAwaitable SwitchToMainThread() {
        return TaskScheduler.SwitchTo();
    }


}

// todo: Can I do it without custom TaskScheduler?
internal class GameTaskScheduler : TaskScheduler {

    private ConcurrentQueue<Task> Tasks { get; } = new ConcurrentQueue<Task>();
    public override int MaximumConcurrencyLevel => 1;

    public void Execute() {
        while (Tasks.TryDequeue( out var task )) {
            TryExecuteTask( task );
        }
    }
    protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued) {
        return false;
    }

    protected override void QueueTask(Task task) {
        Tasks.Enqueue( task );
    }
    protected sealed override bool TryDequeue(Task task) {
        return false;
    }

    protected override IEnumerable<Task>? GetScheduledTasks() {
        return Tasks.ToArray();
    }

}