_addToQueue(args) {
    let ack;
    if (typeof args[args.length - 1] === "function") {
      ack = args.pop();
    }
    const packet = {
      id: this._queueSeq++,
      tryCount: 0,
      pending: false,
      args,
      flags: Object.assign({ fromQueue: true }, this.flags)
    };
    args.push((err, ...responseArgs) => {
      if (packet !== this._queue[0]) {
        return;
      }
      const hasError = err !== null;
      if (hasError) {
        if (packet.tryCount > this._opts.retries) {
          this._queue.shift();
          if (ack) {
            ack(err);
          }
        }
      } else {
        this._queue.shift();
        if (ack) {
          ack(null, ...responseArgs);
        }
      }
      packet.pending = false;
      return this._drainQueue();
    });
    this._queue.push(packet);
    this._drainQueue();
  }
Add the packet to the queue.
@param args
@private