How to proxy requests from vercel Next.Js API to heroku

Question

// next js - [...api]

import httpProxy from "http-proxy";
const BLOG_SERVER = process.env.BLOG_SERVER; // https://example.com
export const config = {
  api: {
    bodyParser: false,
  },
}

export default async function Api(req, res) {
    const proxy = httpProxy.createProxyServer();
    proxy.web(req, res, {
      target: BLOG_SERVER
    });
    proxy.on('error', function (e) {
        console.log(e)
    });
}

The BLOG_SERVER has been hosted at heroku and next.js website has been hosted at vercel.

When i looked at the next.js server logs, then the following are printed.

How can i solve this??