override the default CloseAsync method from websocket session

Author: kerryjiang

src/SuperSocket.WebSocket.Server/WebSocketSession.cs

@@ -130,5 +130,10 @@ public override async ValueTask CloseAsync(ChannelCloseReason closeReason)
 
             }
         }
+
+        public override async ValueTask CloseAsync()
+        {
+            await this.CloseAsync(CloseReason.NormalClosure);
+        }
     }
 }