Keyed service hub example (#228)

* Keyed service hub example

* Keyed service hub example

signalr/hubs/KeyedSvsHub/KeyedSvsHub.csproj

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+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+</Project>

signalr/hubs/KeyedSvsHub/Program.cs

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+using Microsoft.AspNetCore.SignalR;
+
+var builder = WebApplication.CreateBuilder(args);
+
+builder.Services.AddKeyedSingleton<ICache, BigCache>("big");
+builder.Services.AddKeyedSingleton<ICache, SmallCache>("small");
+
+builder.Services.AddRazorPages();
+builder.Services.AddSignalR();
+
+var app = builder.Build();
+
+app.MapRazorPages();
+app.MapHub<MyHub>("/myHub");
+
+app.Run();
+
+public interface ICache
+{
+    object Get(string key);
+}
+public class BigCache : ICache
+{
+    public object Get(string key) => $"Resolving {key} from big cache.";
+}
+
+public class SmallCache : ICache
+{
+    public object Get(string key) => $"Resolving {key} from small cache.";
+}
+
+public class MyHub : Hub
+{
+    public void SmallCacheMethod([FromKeyedServices("small")] ICache cache)
+    {
+        Console.WriteLine(cache.Get("signalr"));
+    }
+
+    public void BigCacheMethod([FromKeyedServices("big")] ICache cache)
+    {
+        Console.WriteLine(cache.Get("signalr"));
+    }
+}

signalr/hubs/KeyedSvsHub/appsettings.json

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+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*"
+}