csharp: Connecting to api server fails with HTTP/2 handshake error

Describe the bug I’m getting the following exception while connecting to my K8s cluster:

System.Net.Http.HttpRequestException: 'An HTTP/2 connection could not be established because the server did not complete the HTTP/2 handshake.'

The code:

KubernetesClientConfiguration config = KubernetesClientConfiguration.BuildConfigFromConfigFile(kubeConfFilePath);
Console.WriteLine($"Connecting to {config.CurrentContext}, {config.Host}, {config.Namespace}, {config.Username}");
config.SkipTlsVerify = true;	//does not change anything
using (IKubernetes client = new Kubernetes(config))
{
	V1NamespaceList namespaces = client.CoreV1.ListNamespace(); //this fails

Whole stacktrace is:

   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()
   at System.Threading.Tasks.TaskCompletionSourceWithCancellation`1.<WaitWithCancellationAsync>d__1.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Threading.Tasks.ValueTask`1.get_Result()
   at System.Runtime.CompilerServices.ConfiguredValueTaskAwaitable`1.ConfiguredValueTaskAwaiter.GetResult()
   at System.Net.Http.HttpConnectionPool.<GetHttp2ConnectionAsync>d__79.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Threading.Tasks.ValueTask`1.get_Result()
   at System.Runtime.CompilerServices.ConfiguredValueTaskAwaitable`1.ConfiguredValueTaskAwaiter.GetResult()
   at System.Net.Http.HttpConnectionPool.<SendWithVersionDetectionAndRetryAsync>d__83.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Threading.Tasks.ValueTask`1.get_Result()
   at System.Runtime.CompilerServices.ConfiguredValueTaskAwaitable`1.ConfiguredValueTaskAwaiter.GetResult()
   at System.Net.Http.RedirectHandler.<SendAsync>d__4.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()
   at System.Net.Http.HttpClient.<<SendAsync>g__Core|83_0>d.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at k8s.Kubernetes.<SendRequestRaw>d__39.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at k8s.AbstractKubernetes.<k8s-ICoreV1Operations-ListNamespaceWithHttpMessagesAsync>d__21.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at k8s.CoreV1OperationsExtensions.<ListNamespaceAsync>d__15.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at k8s.CoreV1OperationsExtensions.ListNamespace(ICoreV1Operations operations, Nullable`1 allowWatchBookmarks, String continueParameter, String fieldSelector, String labelSelector, Nullable`1 limit, String resourceVersion, String resourceVersionMatch, Nullable`1 timeoutSeconds, Nullable`1 watch, Nullable`1 pretty)
   at K8sApiTest.Program.Main(String[] args) in Z:\kube-test\src\K8sApiTest\Program.cs:line 18

Kubernetes C# SDK Client Version 9.0.38

Server Kubernetes Version 1.25.4

Dotnet Runtime Version net6

Expected behavior I expected to be able to connect to the api server

KubeConfig my kubeconf file looks like this:

apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: LS0t...
    server: https://<some_ip>:6443
  name: kubernetes-test
contexts:
- context:
    cluster: kubernetes-test
    user: kubernetes-test-admin
  name: kubernetes-test-admin@kubernetes-test
current-context: kubernetes-test-admin@kubernetes-test
kind: Config
preferences: {}
users:
- name: kubernetes-test-admin
  user:
    client-certificate-data: LS0...
    client-key-data: LS0...

Where do you run your app with Kubernetes SDK (please complete the following information):

• OS: Windows 8.1 Prof
• Environment - just a plain app from MS VS
• Cloud - No

Additional context I doubt that there’s a problem with my kubeconf file, because both Lens and KubeNav have no problems connecting to the API server using the same file.

Here are screenshots from wireshark:

My app with the problem:

Kubenav with no problem:

(black rects mask my machine, green ones mask api server)