next.config.js

const withCSS = require('@zeit/next-css');

module.exports = withCSS({
  webpack(config, { isServer, buildId, dev }) {

    if (isServer) {
      const antStyles = /antd\/.*?\/style\/css.*?/
      const origExternals = [...config.externals]
      config.externals = [
        (context, request, callback) => {
          if (request.match(antStyles)) return callback()
          if (typeof origExternals[0] === 'function') {
            origExternals[0](context, request, callback)
          } else {
            callback()
          }
        },
        ...(typeof origExternals[0] === 'function' ? [] : origExternals),
      ]

      config.module.rules.unshift({
        test: antStyles,
        use: 'null-loader',
      })
    }



    return config;
  },
  publicRuntimeConfig: {
    NODE_ENV: process.env.NODE_ENV
  },
});