Add graceful shutdown using IHostApplicationLifetime

Introduce a mechanism to gracefully stop the application by leveraging the IHostApplicationLifetime interface.

- In BotApp.cs, call StopApplication() on IHostApplicationLifetime after logging that the bot has stopped.
- In BotBuilder.cs, reorganize using directives and register IHostApplicationLifetime as a singleton service.
- Add HostApplicationLifetime.cs to implement IHostApplicationLifetime, providing lifecycle event tokens and a method to stop the application.

Author: bvdcode

Sources/TelegramBot/BotApp.cs

@@ -94,6 +94,8 @@ public void Run(CancellationToken token = default)
                 _logger.LogInformation("Bot stopped - no longer receiving updates.");
             }
             _logger.LogInformation("Stopping hosted services...");
+            var hostApplicationLifetime = _serviceProvider.GetRequiredService<IHostApplicationLifetime>();
+            hostApplicationLifetime.StopApplication();
             foreach (var hostedService in hostedServices)
             {
                 hostedService.StopAsync(token).Wait(token);

Sources/TelegramBot/Builders/BotBuilder.cs

@@ -1,11 +1,13 @@
 using System;
+using System.Linq;
 using Telegram.Bot;
+using TelegramBot.Services;
+using TelegramBot.Providers;
+using TelegramBot.Abstractions;
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
-using System.Linq;
-using TelegramBot.Abstractions;
-using TelegramBot.Providers;
 
 namespace TelegramBot.Builders
 {
@@ -134,6 +136,7 @@ public IBot Build()
             {
                 Services.AddSingleton<IKeyValueProvider, InMemoryKeyValueProvider>();
             }
+            Services.AddSingleton<IHostApplicationLifetime, HostApplicationLifetime>();
             return new BotApp(client, Services.BuildServiceProvider());
         }
     }

Sources/TelegramBot/Services/HostApplicationLifetime.cs

@@ -0,0 +1,23 @@
+using System;
+using System.Threading;
+using Microsoft.Extensions.Hosting;
+
+namespace TelegramBot.Services
+{
+    internal class HostApplicationLifetime : IHostApplicationLifetime
+    {
+        public CancellationToken ApplicationStarted => _cancellationTokenSource.Token;
+
+        public CancellationToken ApplicationStopping => _cancellationTokenSource.Token;
+
+        public CancellationToken ApplicationStopped => _cancellationTokenSource.Token;
+
+
+        private readonly CancellationTokenSource _cancellationTokenSource = new CancellationTokenSource();
+
+        public void StopApplication()
+        {
+            _cancellationTokenSource.Cancel();
+        }
+    }
+}