Can not get files metadata from mongodb as gfs of Gridfs-stream is undefined

node.js mongodb express mongoose gridfs-stream

app.get("/file/:filename", async (req, res) => {    try {        const file = await gfs.files.findOne({ filename: req.params.filename });        const readStream = gfs.createReadStream(file.filename);        readStream.pipe(res);    } catch (error) {        res.send("not found");    }});