How to receive the uploaded stream with fetch() upload stream ?

[gtk2k]

https://chromestatus.com/feature/5274139738767360

In express, I can get stream data with

app.post('/upload', (req, res) => {
  req.on('data', (chunk) => {
    //
  });
});

How can I get stream data in Koa.js?

[jonathanong]

ctx.req.on('data', (chunk) => {})