Add Shutdown(CancellationToken token)

Author: yannickcholette

src/Client/LanguageClient.cs

@@ -420,10 +420,20 @@ private void RegisterCapabilities(ClientCapabilities capabilities)
         }
 
         public async Task Shutdown()
+        {
+            await Shutdown(CancellationToken.None);
+        }
+
+        public async Task Shutdown(CancellationToken token)
         {
             if (_connection.IsOpen)
             {
-                await this.RequestShutdown().ConfigureAwait(false);
+                try
+                {
+                    await this.RequestShutdown(token).ConfigureAwait(false);
+                }
+                catch (TaskCanceledException) { }
+
                 this.SendExit();
             }