code: function subscribe(topic, roomId) {
      return new Promise((resolve, reject) => {
          log_1.logger.info(`[subscribe] Preparing subscription: ${topic}: ${roomId}`);
          const subscription = exports.asteroid.subscribe(topic, roomId, true);
          exports.subscriptions.push(subscription);
          return subscription.ready
              .then((id) => {
              log_1.logger.info(`[subscribe] Stream ready: ${id}`);
              resolve(subscription);
          });
      });
  }
docs: Subscribe to Meteor subscription
  Resolves with subscription (added to array), with ID property
  @todo - 3rd param of asteroid.subscribe is deprecated in Rocket.Chat?