gistfile1.cs

    class Program
    {
        static void Main(string[] args)
        {
            Run().Wait();
        }

        static async Task Run()
        {            
            var tcs = new TaskCompletionSource<object>();
            Task t1 = null;
            Console.WriteLine("1:" + Environment.CurrentManagedThreadId);
            t1 = Task.Factory.StartNew(() =>
                {
                    Console.WriteLine("2:" + Environment.CurrentManagedThreadId);
                    System.Threading.Thread.Sleep(1000);
                    tcs.SetResult(null);
                }
            );

            Console.WriteLine("3:" + Environment.CurrentManagedThreadId);
            await tcs.Task;
            Console.WriteLine("4:" + Environment.CurrentManagedThreadId);
            t1.Wait();
        }
    }