stream.push() after EOF

[dlebedynskyi]

Hi, occasionally getting following error

Error: stream.push() after EOF 

sometime also seeing

TypeError: Cannot read property 'write' of null
  File "zlib.js", line 469, col 32, in Zlib.callback

only package we use that references zlib is koa-compress with next config
configuration

app.use(compress({
  flush: require('zlib').Z_SYNC_FLUSH
}))

using node 8.

Any idea on why this happens and how to fix this?

[haoxins]

duplicated with #60 :)