Use Pipelines in PlaintextApp sample

src/Servers/Kestrel/samples/PlaintextApp/Startup.cs

@@ -1,12 +1,16 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.IO;
+using System.IO.Pipelines;
 using System.Net;
+using System.Runtime.CompilerServices;
 using System.Text;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Http;
 
 namespace PlaintextApp
 {
@@ -16,16 +20,19 @@ public class Startup
 
         public void Configure(IApplicationBuilder app)
         {
-            app.Run((httpContext) =>
-            {
-                var response = httpContext.Response;
-                response.StatusCode = 200;
-                response.ContentType = "text/plain";
-
-                var helloWorld = _helloWorldBytes;
-                response.ContentLength = helloWorld.Length;
-                return response.Body.WriteAsync(helloWorld, 0, helloWorld.Length);
-            });
+            app.Run(Plaintext);
+        }
+
+        private static Task Plaintext(HttpContext httpContext)
+        {
+            var payload = _helloWorldBytes;
+            var response = httpContext.Response;
+
+            response.StatusCode = 200;
+            response.ContentType = "text/plain";
+            response.ContentLength = payload.Length;
+
+            return response.BodyPipe.WriteAsync(payload).GetAsTask();
         }
 
         public static Task Main(string[] args)
@@ -42,4 +49,22 @@ public static Task Main(string[] args)
             return host.RunAsync();
         }
     }
+
+    internal static class ValueTaskExtensions
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Task GetAsTask<T>(this in ValueTask<T> valueTask)
+        {
+            if (valueTask.IsCompletedSuccessfully)
+            {
+                // Signal consumption to the IValueTaskSource
+                valueTask.GetAwaiter().GetResult();
+                return Task.CompletedTask;
+            }
+            else
+            {
+                return valueTask.AsTask();
+            }
+        }
+    }
 }