express js asset proxy route

assets.js

router.get(
  "/:asset_type/:space_id/:asset_id/:token/:name",
  async (req, res, next) => {
    const format = req.query.fm;
    const width = req.query.w;

    const { asset_type, space_id, asset_id, token, name } = req.params;

    res.locals.fetchUrl = `https://${asset_type}.ctfassets.net/${space_id}/${asset_id}/${token}/${name}?fm=${format}${
      width ? `&w=${width}` : ""
    }`;

    res.locals.cacheKey = `${token}/${name}/${format}/${width}`;

    next();
  },
  fileCacheMiddleware({ cacheDir, logger }),
  (req, res) => {
    res.set({
      "Content-Type": res.locals.contentType,
      "Content-Length": res.locals.contentLength
    });
    res.end(res.locals.buffer, "binary");
  }
);