title: AngularFire2 - Cannot find module @firebase/database
body: <p>I've installed and used AngularFire2 a lot of times for projects, but since the release of v5, I can't set it up correctly.</p>
  
  <p>These are the steps I follow to reach the issue.</p>
  
  <pre><code>$ ionic start angularfire2test tabs
  $ npm install angularfire2 firebase --save
  </code></pre>
  
  <p>package.json</p>
  
  <pre><code>"angularfire2": "^5.0.0-rc.3",
  "firebase": "^4.5.2",
  </code></pre>
  
  <p>Add Firebase credentials to app.module.ts + import default module and database module. This is the most important part</p>
  
  <pre><code>import { AngularFireModule } from 'angularfire2';
  import { AngularFireDatabaseModule } from 'angularfire2/database';
  ...
  @NgModule({
    declarations: [
      MyApp,
      AboutPage,
      ContactPage,
      HomePage,
      TabsPage
    ],
    imports: [
      BrowserModule,
      IonicModule.forRoot(MyApp),
      AngularFireModule.initializeApp(firebaseCredentials),
      AngularFireDatabaseModule
    ],
    bootstrap: [IonicApp],
    entryComponents: [
     ....
  </code></pre>
  
  <p>When I execute <code>$ ionic serve</code>, I get the error message "Cannot find module "@firebase/database"  at webpackMissingModule (<a href="http://localhost:8100/build/vendor.js:119190:82" rel="noreferrer">http://localhost:8100/build/vendor.js:119190:82</a>)</p>
  
  <p>When checking the node_modules folder, @firebase doesn't have a database subfolder, but the firebase-folder does have a database-folder.</p>
  
  <p>Did I do something wrong or is it a general issue with AngularFire2?</p>