how add config by env vars in next.js

index.html

<script>
  const configValues = document.cookie.split('; ').find(c => c.startsWith('config')).split('=')[1]
  const config = JSON.parse(window.unescape(config))
</scrip>

middleware.js

module.exports = (req, res, next) => {
    res.cookie("config",  JSON.stringify({ endpoint: process.env.END_POINT  || "https://localhost:3000" }));
    next();
});