Geoserver giving error 504 when accessed using NodeJs but not in postman

Question

few points to consider:

1. I have a proxy server enabled on my system, its IP is 192.18.x.x:8080
2. I needs to be logged in so the creds are johndoe:john_1234
3. I am using geoserver which is running at port 8085 of my machine

problem:

whenever I am trying to make a get request to the url "http://localhost:8085/geoserver/rest" programmatically using NodeJS, Python, Bash and even by Curl, I am getting a 504 error

but when I am making the same request using postman, there is no error and I am getting the desired output

here is the basic code I am using:

const http = require('http');

// Proxy server details
const proxyHost = '192.168.x.x';
const proxyPort = 8080;
const proxyUsername = 'johndoe';
const proxyPassword = 'john_1234';

// Target URL you want to request
const targetUrl = 'http://localhost:8085/geoserver/rest';

// Construct the proxy authorization header
const proxyAuthHeader = `Basic ${Buffer.from(`${proxyUsername}:${proxyPassword}`).toString('base64')}`;

// Options for the HTTP request
const options = {
  hostname: proxyHost,
  port: proxyPort,
  path: targetUrl,
  method: 'GET',
  headers: {
    'Proxy-Authorization': proxyAuthHeader,
  },
};

// Make the request through the proxy
const req = http.request(options, (res) => {
  let data = '';

  res.on('data', (chunk) => {
    data += chunk;
  });

  res.on('end', () => {
    console.log(data);
  });
});

req.on('error', (error) => {
  console.error('Error:', error);
});

req.end();

why is it working fine in postman and it also gives the error of method not allowed