Hi, @minho-comcom-ai
Could you please explain in which cases this feature is needed?

Hello, @stegano!
The purpose of this PR is to add headers (such as tracing) dynamically on each requests by following this http-proxy document.
There are headers option already in http-proxy, but it was globally affected to the same headers on every requests, not each requests.

@minho-comcom-ai
Thanks for the explanation.

Adding header information dynamically to each request can be solved without modifying this library.

export default (req: NextApiRequest, res: NextApiResponse) => {
  if (req.url === '/api/test') {
    // Adding request headers dynamically
    req.headers['your-proxy-header'] = 'test';
  }
  nextHttpProxyMiddleware(req, res, {
    target: 'http://127.0.0.1:8099',
    pathRewrite: {
      '^/api': '',
    },
  });
};

And if you use the 'proxyReqOverride' you suggested, you won't be able to deal with the problem in #3.
Please let me know if I'm wrong.
Thank you 😀

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