BackgroundService not stopping gracefully with an open Blazor Server SignalR circuit on dotnet 9

[previato]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

The BackgroundService stoppingToken is not triggering instantly when there is a browser session open with a Blazor Server interactive page.

The gracefully shutdown is not happening as expected when doing a Ctrl+C on Console.

The same code work as expected on .net 8

If you navigate to a statically rendered page, the issue does not happens.

// Program.cs
var builder = WebApplication.CreateBuilder(args);

builder.Services.AddRazorComponents()
    .AddInteractiveServerComponents();

builder.Services.AddHostedService<Job>();

var app = builder.Build();

if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error", createScopeForErrors: true);
    app.UseHsts();
}

app.UseHttpsRedirection();

app.UseAntiforgery();

app.MapStaticAssets();
app.MapRazorComponents<App>()
    .AddInteractiveServerRenderMode();

app.Run();

// Job.cs
public class Job(ILogger<Job> logger) : BackgroundService
{
    protected override Task ExecuteAsync(CancellationToken stoppingToken)
    {
        return Task.Run(async () =>
        {
            stoppingToken.Register(() =>
            {
                // The code here is not calling immediately when Ctrl+C is pressed.
                logger.LogInformation("Job is stopping");
            });

            while (!stoppingToken.IsCancellationRequested)
            {
                logger.LogInformation("Job is running");
                await Task.Delay(1000);
            }
        }, stoppingToken);
    }
}

Expected Behavior

The stoppingToken of all Hosted Service should trigger immediately.

Steps To Reproduce

• Create a new .net 9.0 Blazor Web App Project, choose Interactive render mode = Server and Interactivity location = Global
• Create a background job which inherits from BackgroundService and register it on Program.cs
• Create a while loop on the background service which should stop doing their job when application is closing
• Execute the program and leave a page open on Browser which create a SignalR Blazor circuit

Exceptions (if any)

No response

.NET Version

9.0.101

Anything else?

No response

[BrennanConroy]

Should be same root cause as #58947 (comment)
You can work around it by modifying the reconnection logic to wait a little before the first reconnect attempt https://learn.microsoft.com/aspnet/core/blazor/fundamentals/signalr?view=aspnetcore-9.0#adjust-the-server-side-reconnection-retry-count-and-interval

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