Can't pipe a stream to ctx.res from http.get

[simongcc]

I am trying pipe a stream with an image url to ctx.res.
It could be done using http.createServer so I try to do the same in Koa but it doesn't seems to work.
I think it could be the timing problem. However, I have tried many patterns of await/sync, new Promise resolver and so on.
Still can't seems to get the steam to ctx.body.

Image from url

This is a simple version with image url using nodejs http get.
It shows 'Not Found' because ctx.body did not get update before it respond to the browser.

const http = require('http');
const koa = require('koa');
const fs = require('fs');

const app = new koa();

app.use(async (ctx) => {
    const imageUrl = 'http://127.0.0.1/some_image.jpg';

    // Test Result: Not Found
    http.get(imageUrl, async (imageStream) => {
        ctx.response.set('Content-Type', imageStream.headers['content-type']);
        const { statusCode, headers } = imageStream;
        // console.log(statusCode); // 200
        // console.log(headers); // content=type is image/jpeg, content-length confirmed same as the original file.
        await imageStream.pipe(ctx.res);
        ctx.body = imageStream;
    });
});

app.listen(8080);

http version By piping the image readStream to response writeStream, it serves the image.

const http = require('http');

const port = 8080;

const downloadUrl = 'http://127.0.0.1/some_image.jpg';

http.createServer(options, (req, res) => {
    http.get(downloadUrl, (stream) => {
        // console.log(stream);
        stream.pipe(res);
    });
  }).listen(port);

I wonder how should I get it done using Koa to serve the images.
Because the program is commonJS based, I have considered got library but it completely remove support of commonJS.

Any help is appreciated.

[simongcc]

A quick update to the question.
I found the follow works without piping it.
Because in the source code of koa application.js
it is

if (body instanceof Stream) return body.pipe(res);

So it is not necessary to pipe for Koa, Koa will handle it.
And thus

 await imageStream.pipe(ctx.res); => //  await imageStream.pipe(ctx.res); Not necessary

But then I found another problem.
If the stream originally controlled by authenticated source. This is not working.
I will continue to study. If any one knows could share their insight. Much thanks.