using System;

using System.Threading;

using System.Threading.Tasks;

using System.Diagnostics;

​

static public class Program

{

    static private object _lock = new object();

    static private TaskCompletionSource<bool> _tcs = new TaskCompletionSource<bool>();

    static public void Main()

    {

        Test().Wait();

    }

​

    private static async Task Test()

    {

        var task = ItWillContinueInsideLock();

        lock(_lock)

        {

            Console.WriteLine("Entering lock");

            _tcs.SetResult(true);

            Console.WriteLine("Exiting lock");          

        }

        await task;

    }

    private static async Task ItWillContinueInsideLock()

    {

        await _tcs.Task;

        Console.WriteLine("I'm running inside lock");

    }

}