fix SignalR http2 SkipNegotiation error

[WeihanLi]

fix SignalR http2 SkipNegotiation error

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Description

Creating HttpClient for WebSocket SkipNegotiation mode also

Fixes #59303

[Copilot]

Pull Request Overview

This PR fixes an issue where SignalR clients using HTTP/2 with SkipNegotiation mode were not properly creating an HttpClient, which caused errors. The fix ensures that HttpClient is always created regardless of the negotiation and transport settings.

• Removes conditional logic that prevented HttpClient creation in certain scenarios
• Ensures HttpClient is available for all transport configurations

Comments suppressed due to low confidence (1)

src/SignalR/clients/csharp/Http.Connections.Client/src/HttpConnection.cs:151

• The removal of the conditional logic that prevented HttpClient creation in SkipNegotiation + WebSockets-only scenarios should be covered by tests to ensure this fix works correctly and prevent regression.

        _httpClient = CreateHttpClient();

[JakubTracz]

Hi, any progress in fixing this?

[WeihanLi]

I verified locally, but not sure if that's the way the team wants to adopt and not sure about the test cases that should be added
@BrennanConroy could you please help suggest

[BrennanConroy]

Can you update the _httpClient field to be non-nullable, fix the NegotiateAsync call to not use !, and not use ? in the Dispose call?

[BekAllaev]

Hello, is this PR still active?
I would like to help move this one, if it works with you @WeihanLi.
It looks like the remaining changes might include:

1. Remove nullability here:
   https://github.com/WeihanLi/aspnetcore/blob/2ac1414904456637280d9d4fbf99ac05843b8515/src/SignalR/clients/csharp/Http.Connections.Client/src/HttpConnection.cs#L45
2. Therefore removing ! here:
   https://github.com/WeihanLi/aspnetcore/blob/2ac1414904456637280d9d4fbf99ac05843b8515/src/SignalR/clients/csharp/Http.Connections.Client/src/HttpConnection.cs#L714
   And removing ? here:
   https://github.com/WeihanLi/aspnetcore/blob/2ac1414904456637280d9d4fbf99ac05843b8515/src/SignalR/clients/csharp/Http.Connections.Client/src/HttpConnection.cs#L287

Please let me know if I can help with this one @WeihanLi @BrennanConroy