http-proxy-middleware.ts Return promise to wait end of connection

[desfun]

It allows koajs handle http-proxy-middleware, awaiting end of transaction from proxy, if you don't handle it, response will be emitted before end of proxy request.

Description

Allow handle propperly end of remote connection before emit response to client.

Motivation and Context

Koajs compability

How has this been tested?

const app = new koa(); app.use(async ({req,res},next)=>{ const Proxy = createProxyMiddleware(options); await Proxy(req,res,next); }});

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [X] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.

[chimurai]

Doesn't look like valid implementation.

Runtime error:

Feel free to update PR if working implementation + test can be provided