public hosting_on_kestrel()
        {
            server =
                new WebHostBuilder()
                .UseKestrel()
                .UseUrls($"http://127.0.0.1:0")
                .Configure(app => app.UseOpenRasta(new TaskApi()))
                .Build();

            server.Start();
            var port = server.Port();

            client = new HttpClient {
                BaseAddress = new Uri($"http://localhost:{port}")
            };
        }