왜 무한로딩이 될까요...

router.post("/getVideoDetail", (req, res) => {
  Video.findOne({ _id: req.body.videoId })
    // populate = bring every info from writer
    .populate("writer")
    .exec((err, videoDetail) => {
      if (err) return res.status(400).json({ success: false, err });
      res.status(200).json({ success: true, videoDetail });
    });
});