Simple Nowin app with middleware

Program.cs

using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Threading.Tasks;
using Nowin;

namespace HelloNowin
{
    using AppFunc = Func<IDictionary<string, object>, Task>;

    class Program
    {
        static void Main(string[] args)
        {
            AppFunc app = env =>
            {
                var responseBytes = System.Text.Encoding.UTF8.GetBytes(
                    string.Format("Serviced request on {0} at {1}", DateTime.Now.ToLongDateString(),
                        DateTime.Now.ToLongTimeString()));

                Stream responseStream = (Stream)env["owin.ResponseBody"];
                IDictionary<string, string[]> responseHeaders =
                    (IDictionary<string, string[]>)env["owin.ResponseHeaders"];
                responseHeaders["Content-Length"] = new string[] { responseBytes.Length.ToString(CultureInfo.InvariantCulture) };
                responseHeaders["Content-Type"] = new string[] { "text/plain" };
                return responseStream.WriteAsync(responseBytes, 0, responseBytes.Length);
            };

            AppFunc appWithMiddleWare = env =>
            {
                var responseBytes = System.Text.Encoding.UTF8.GetBytes(
                    string.Format("Some middleware {0} at {1} {2}", DateTime.Now.ToLongDateString(),
                        DateTime.Now.ToLongTimeString(), Environment.NewLine));
                Stream responseStream = (Stream) env["owin.ResponseBody"];
                responseStream.WriteAsync(responseBytes, 0, responseBytes.Length);
                return app(env);
            };

            var serverBuilder = ServerBuilder.New().SetPort(1337).SetOwinApp(appWithMiddleWare);
            using (serverBuilder.Start())
            {
                Console.WriteLine("Listening on port 1337");
                Console.ReadLine();
            }
        }
    }
}