using System;

using System.Collections.Generic;

using System.Linq;

using System.Threading.Tasks;

​

public class Program

{

    static async Task Main()

    {

        await foreach (var item in GetStream().Take(1))

        {

            Console.WriteLine($"Received: {item}");

        }

        Console.WriteLine($"Done");

    }

​

    static async IAsyncEnumerable<int> GetStream()

    {

        var locker = new object();

        await Task.Delay(100);

        try

        {

            yield return 1;

            yield return 2;

        }

        finally

        {

            Console.WriteLine($"Finally before lock");

            lock (locker) { }

            Console.WriteLine($"Finally after lock");

        }

    }

}

​