Here is what our default worker.js file includes
importScripts("https://storage.googleapis.com/workbox-cdn/releases/5.1.2/workbox-sw.js");
if (workbox) {
workbox.setConfig({
debug: false,
});
workbox.loadModule("workbox-core");
workbox.loadModule("workbox-precaching");
workbox.loadModule("workbox-strategies");