// Criar um Console no Visual Studio 

// .NET Framework 4.6.1

​

using System;

using System.Threading.Tasks;

using System.Threading;

using System.Diagnostics;

​

public class Program

{

    public static void Main(string[] args)

    {

        MetodoAsync();

​

        Thread.Sleep(1000);

        Console.WriteLine("Teste1");

        Thread.Sleep(1000);

        Console.WriteLine("Teste2");

        Thread.Sleep(1000);

        Console.WriteLine("Teste3");

​

        Console.ReadLine();

    }

    private static async void MetodoAsync()

    {

        var sw = new Stopwatch();

        sw.Start();

        string letras = await RetornarString();

        sw.Stop();

        Console.WriteLine("Tempo Gasto (ms): " + sw.ElapsedMilliseconds.ToString());

        Console.WriteLine(letras);

    }

    private static Task<string> RetornarString()

    {

        return Task.Run(() =>

        {

            Thread.Sleep(5000);

            return "String de Retorno";

        });

    }

}