using System;

using System.Threading.Tasks;

public class Program

{

    public static async Task Main()

    {

        var monitor = new ReentrantAsyncLock.ReentrantAsyncLock();

        async Task Func1(int i)

        {

            if (i == 0) { return; }

            await using (await monitor.LockAsync(default))

            {

                await Func2(i-1);

            }

        }

​

        async Task Func2(int i)

        {

            if (i == 0) { return; }

            await using (await monitor.LockAsync(default))

            {

                await Func1(i-1);

            }

        }

​

        // First example

        await Func1(42);

        // Second example

        await Task.WhenAll(Func1(42), Func2(42));

        Console.WriteLine("Done");

    }

}