next.config.js

const withOffline = require('next-offline')

module.exports = withOffline({
	exportPathMap: function() {
		return {
			'/': { page: '/' }
		};
	},
	webpack: config => {
		config.externals = [
			'/'
		]
		return config
	},
	target: process.env.NEXT_TARGET || 'serverless',
	workboxOpts: {
		swDest: 'static/service-worker.js',
		runtimeCaching: [
			{
				urlPattern: /[.](png|jpg|ico|css)/,
				handler: 'CacheFirst',
				options: {
					cacheName: 'assets-cache',
					cacheableResponse: {
						statuses: [0, 200]
					}
				}
			},
			{
				urlPattern: /^https:\/\/code\.getmdl\.io.*/,
				handler: 'CacheFirst',
				options: {
					cacheName: 'lib-cache'
				}
			},
			{
				urlPattern: /^http.*/,
				handler: 'NetworkFirst',
				options: {
					cacheName: 'http-cache'
				}
			}
		]
	}
})