S3 limiting file size based on fieldName on upload.fields

I want to be able to filter files based on different file extensions. One idea would be to pass a middleware after the upload which handles it. Like this:

```javascript
app.post("/upload", S3.upload.fields([{
name: 'video',
maxCount: 1,
}, {
name: 'subtitles',
maxCount: 1,
}]), validateUploadForms, validateUploadSizes, async function(req, res, next) {

console.log("Success");

});

function validateUploadSizes(req, res, next) {

if (req.files.video[0].size > 2000) {
return next();
} else {

res.json({
response: Strings.ERROR
});

return next(new Error);

}

}
```

But the problem here is that the file is already finished uploading so I will have to waste extra space and time on removing it.

Another idea would be to do something like this:

```javascript
app.post("/upload", S3.upload.single("video"), S3.upload.single("audio"), validateUploadForms, async function(req, res, next) {

console.log("Success");

});
```

And then use the `fieldSize`/`fileSize` property. But I am unsure on how it would work like. The problem here is that I can't use multiple `upload.single` middlewares.

What can I do? I am using S3/MulterS3