node.js express无法通过流上传文件

router.post("/upload", function(req, res, next) {
    var form = new multiparty.Form();
    form.on("part", function(part) {
        if (!part.filename) {
            part.resume();
            return;
        }

        var fd = new FormData();
        fd.append("upload", part);
        fd.submit(storageUrl, function(err, res0) {
            if (err) {
                console.error(err);
                res.status(500);
            }

            res.end();
        });
    });

    form.parse(req);
});router.post("/upload", function(req