next.config.js

const withPlugins = require('next-compose-plugins');
const path = require('path');

module.exports = withPlugins([], {
  webpack: (config) => {
    const clientEnv = process.env.CLIENT_ENV || 'production';

    config.resolve.alias = {
      ...config.resolve.alias,
      environment: path.join(__dirname, 'src', 'environments', clientEnv),
    };

    return config;
  },
});