add generic watch (#1155)

* add generic watch

* Update WatcherExt.cs

Author: tg123

src/KubernetesClient/GenericClient.cs

@@ -115,6 +115,34 @@ public async Task<T> ReplaceNamespacedAsync<T>(T obj, string ns, string name, Ca
             return KubernetesJson.Deserialize<T>(resp.Body.ToString());
         }
 
+        public IAsyncEnumerable<(WatchEventType, T)> WatchAsync<T>(Action<Exception> onError = null, CancellationToken cancel = default)
+        where T : IKubernetesObject
+        {
+            var respTask = kubernetes.CustomObjects.ListClusterCustomObjectWithHttpMessagesAsync(group, version, plural, watch: true, cancellationToken: cancel);
+            return respTask.WatchAsync<T, object>();
+        }
+
+        public IAsyncEnumerable<(WatchEventType, T)> WatchNamespacedAsync<T>(string ns, Action<Exception> onError = null, CancellationToken cancel = default)
+        where T : IKubernetesObject
+        {
+            var respTask = kubernetes.CustomObjects.ListNamespacedCustomObjectWithHttpMessagesAsync(group, version, ns, plural, watch: true, cancellationToken: cancel);
+            return respTask.WatchAsync<T, object>();
+        }
+
+        public Watcher<T> Watch<T>(Action<WatchEventType, T> onEvent, Action<Exception> onError = null, Action onClosed = null)
+        where T : IKubernetesObject
+        {
+            var respTask = kubernetes.CustomObjects.ListClusterCustomObjectWithHttpMessagesAsync(group, version, plural, watch: true);
+            return respTask.Watch(onEvent, onError, onClosed);
+        }
+
+        public Watcher<T> WatchNamespaced<T>(string ns, Action<WatchEventType, T> onEvent, Action<Exception> onError = null, Action onClosed = null)
+        where T : IKubernetesObject
+        {
+            var respTask = kubernetes.CustomObjects.ListNamespacedCustomObjectWithHttpMessagesAsync(group, version, ns, plural, watch: true);
+            return respTask.Watch(onEvent, onError, onClosed);
+        }
+
         public void Dispose()
         {
             Dispose(true);

src/KubernetesClient/WatcherExt.cs

@@ -1,6 +1,7 @@
 using k8s.Autorest;
 using k8s.Exceptions;
 using System.IO;
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace k8s
@@ -72,12 +73,14 @@ public static Watcher<T> Watch<T, L>(
         /// <typeparam name="L">type of the HttpOperationResponse object</typeparam>
         /// <param name="responseTask">the api response</param>
         /// <param name="onError">a callbak when any exception was caught during watching</param>
+        /// <param name="cancellationToken">cancellation token</param>
         /// <returns>IAsyncEnumerable of watch events</returns>
         public static IAsyncEnumerable<(WatchEventType, T)> WatchAsync<T, L>(
             this Task<HttpOperationResponse<L>> responseTask,
-            Action<Exception> onError = null)
+            Action<Exception> onError = null,
+            CancellationToken cancellationToken = default)
         {
-            return Watcher<T>.CreateWatchEventEnumerator(MakeStreamReaderCreator<T, L>(responseTask), onError);
+            return Watcher<T>.CreateWatchEventEnumerator(MakeStreamReaderCreator<T, L>(responseTask), onError, cancellationToken);
         }
     }
 }