Merge pull request #8850 from Hadoukanen/master

Added optional callback for close function

ws/ws.d.ts

@@ -110,7 +110,7 @@ declare module "ws" {
 
             constructor(options?: IServerOptions, callback?: Function);
 
-            close(): void;
+            close(cb?: () => {}): void;
             handleUpgrade(request: http.ServerRequest, socket: net.Socket,
                           upgradeHead: Buffer, callback: (client: WebSocket) => void): void;