_app.js

// pages/_app.js

import React from 'react'

import CookiesUtils from '../utils/cookies'

const App = () => {
  // ...
}

App.getInitialProps = async ({ ctx }) => {
  // ...

  CookiesUtils.setServerSideCookies(ctx)

  CookiesUtils.setItem('server-side-cookies', 'Aloha from server side cookies!')

  CookiesUtils.getItem('server-side-cookies') // Output: Aloha from server side cookies!

  // ...
}

export default App