How to do api calls without fetch in nextjs?

I have a NextJS project with express backend that requires some data fetching in getServerSideProps.

The problem is await fetch('/api/anyApi') does not work with relative path and calls to absolute path await fetch('${config.OPTION_HOST}/api/anyApi' are getting blocked by some kind of protection on host machine.

I wish to fix this problem instead and just use absolute paths but I've been told that's not possible right now so I need to rewrite getServerSideProps everywhere to not use fetch.

Best solution I could find without rewriting big chunk of backend logic was to use mocks like in this anwser.

So instead of const result = await fetch('/api/menu/${context.locale}'), I ended up with this code:

export async function getServerSideProps(context) {
  
  const categoryController = require('../../../server/controllers/category')
  
  var MockExpressRequest = require('mock-express-request');
  var MockExpressResponse = require('mock-express-response');

  var requestMenu = new MockExpressRequest( {
    params: {
      locale: context.locale,
    }
  })
  var responseMenu = new MockExpressResponse();

  await categoryController.getCategories(requestMenu, responseMenu);

  const result = responseMenu

...rest of getServerSideProps...
}

I'm new to programing and while this solution works, I have a feeling that using a library for testing in production code might be bad idea. What do you think?