Socket hang up
I am making a koa server, I having socket hang up issue when I trying to call the server with chunked encoding inside the header. It is working fine when I remove the 'transfer-encoding': 'chunked' in the request header. Thank you for help.

```
// Server code
const Koa = require('koa');
const Router = require('koa-router');
const app = module.exports = new Koa();

class Controller extends Router {
    constructor() {
        super();

        super.post('/post', this.function);
    }

    function(context) {
        Object.assign(context.response, {
            body: 'Posted',
            status: 201,
        });
    }
}


const router = new Router();
const controller = new Controller();

router.use(controller.routes(), controller.allowedMethods());
app.use(router.routes());

if (!module.parent) app.listen(8000);

//Client code
const option = {
    url: 'http://localhost:8000/post',
    method: 'POST',
    headers: {
        'transfer-encoding': 'chunked',
    },
  };


  const request = require('request');
  request(option, (error, response, body) => {
      console.log(response && response.body);
      console.log(error && error.message);
  });
```