Default to HTTP/2 on net5

Author: brendandburns

src/KubernetesClient/Kubernetes.ConfigInit.cs

@@ -170,7 +170,6 @@ private void CreateHttpClient(DelegatingHandler[] handlers, KubernetesClientConf
         {
             FirstMessageHandler = HttpClientHandler = CreateRootHandler();
 
-
 #if NET5_0
             // https://github.com/kubernetes-client/csharp/issues/587
             // let user control if tcp keep alive until better fix
@@ -187,7 +186,12 @@ private void CreateHttpClient(DelegatingHandler[] handlers, KubernetesClientConf
                 //
                 // Should remove after better solution
 
-                var sh = new SocketsHttpHandler();
+                var sh = new SocketsHttpHandler
+                {
+                    KeepAlivePingPolicy = HttpKeepAlivePingPolicy.WithActiveRequests,
+                    KeepAlivePingDelay = new TimeSpan(0, 3, 0),    // Send pings every three minutes
+                    KeepAlivePingTimeout = new TimeSpan(0, 0, 30), // Timeout pings after 30s of no response
+                };
                 sh.ConnectCallback = async (context, token) =>
                 {
                     var socket = new Socket(SocketType.Stream, ProtocolType.Tcp)
@@ -243,6 +247,10 @@ private void CreateHttpClient(DelegatingHandler[] handlers, KubernetesClientConf
 
             AppendDelegatingHandler<WatcherDelegatingHandler>();
             HttpClient = new HttpClient(FirstMessageHandler, false);
+
+#if NET5_0
+            HttpClient.DefaultRequestVersion = HttpVersion.Version20;
+#endif
         }
 
         /// <summary>