fix: Handle rejected when open a webhook in a port that was already i…

…n use

Co-authored-by: windka <karl-heinz.wind.external@trumpf.com>

src/telegramWebHook.js

@@ -45,17 +45,21 @@ class TelegramBotWebHook {
   /**
    * Open WebHook by listening on the port
    * @return {Promise}
-   */
+   */  
   open() {
     if (this.isOpen()) {
       return Promise.resolve();
     }
-    return new Promise(resolve => {
+    return new Promise((resolve, reject) => {
       this._webServer.listen(this.options.port, this.options.host, () => {
         debug('WebHook listening on port %s', this.options.port);
         this._open = true;
         return resolve();
       });
+
+      this._webServer.once('error', (err) => {
+        reject(err);
+      });
     });
   }