server.js

var Bot = require('node-telegram-bot-api')
var watson = require('watson-developer-cloud');
var request = require('request');
var config = require('./config');

var speech_to_text = watson.speech_to_text({
  username : config.watson.username,
  password : config.watson.password,
  version : 'v1',
  url : 'https://stream.watsonplatform.net/speech-to-text/api'
});

var params = {
  content_type : 'audio/ogg;codecs=opus',
  continuous : true,
  interim_results : false
};

var bot = new Bot(config.telegram.token, { polling : true });

bot.on('message', function (msg) {
  if (msg['voice']) { return onVoiceMessage(msg); }
});

function onVoiceMessage(msg) {
  var chatId = msg.chat.id;
  bot.getFileLink(msg.voice.file_id).then(function(link) {
    //setup new recognizer stream
    var recognizeStream = speech_to_text.createRecognizeStream(params);
    recognizeStream.setEncoding('utf8');
    recognizeStream.on('results', function(data) {
    if (data && data.results && data.results.length > 0 && data.results[0].alternatives && data.results[0].alternatives.length > 0) {
      var result = data.results[0].alternatives[0].transcript;
      console.log('result: ', result);

      //send speech recognizer result back to chat
      bot.sendMessage(chatId, result, {
        disable_notification : true,
        reply_to_message_id : msg.message_id
      }).then(function () {
        // reply sent!
      });
    }

  });
    ['data', 'error', 'connection-close'].forEach(function(eventName) {
      recognizeStream.on(eventName, console.log.bind(console, eventName + ' event: '));
    });

    //pipe voice message to recognizer -> send to watson
    request(link).pipe(recognizeStream);
  });
}