Performance issue while returning a large Object
I have a 1.7MB object to send.

Doing this will cause a *TTFB* time of 330ms (that's ok) and a *Content download* time of 4s in Chrome.
```javascript
router.get('/heavy', async function heavyRoute(ctx, next) {
  const result = await collectHeavyData()
  ctx.body = result // my 1.7MB object
  console.log('less than 100ms and we are here')
})
```

The same logic written with .NET cause a *TTFB* time of 2s (that's ok, my bad) and a *Content download* time of **92ms**.

The response are the same, the Koa route code execute in less than 100ms, but the client get the complete response really slowly.

Am I missing something?