title: PWA Workbox App not working when offline
body: <p>Things seem to be working fine when the app is online, I can navigate between pages and files seem to be cached properly. But when I make the browser offline, the app doesn't load.</p>
  
  <p>I get this error:</p>
  
  <pre><code>This site can’t be reached
  The web page at http://localhost:8080/ might be temporarily down or it may 
  have moved permanently to a new web address.
  ERR_FAILED
  </code></pre>
  
  <p>In the console I get this error:</p>
  
  <pre><code>The FetchEvent for "http://localhost:8080/" resulted in a network error 
  response: the promise was rejected.
  Promise.catch (async)
  workbox.precaching.moduleExports.addRoute.self.addEventListener.event @ 
  workbox-precaching.dev.js:1085
  sw.js:1 Uncaught (in promise) TypeError: Failed to fetch
  </code></pre>
  
  <p>I think the last line is the culprit, somehow its not loading the precache manifest file:</p>
  
  <pre><code>importScripts("precache-manifest.2e5a7cbc2c0451bb1e36932f58b5075b.js", "https://storage.googleapis.com/workbox-cdn/releases/3.2.0/workbox-sw.js");
  </code></pre>
  
  <p>The precache manifest file appears in console in the Sources -> Network Tab under the sw.js file category, whilst online. So I'm assuming that somehow this file isn't cached or saved for when the app becomes offline. I've followed the webpack tutorial and didn't seem to find anything that tells the <code>precache-manifest</code> file to be stored. That file doesn't even appear in the Application tab (console) -> Cache -> Cache Storage -> my-app-runtime (or the precached version)</p>