title: Check for existing key in AsyncStorage
body: <p>I want to display the right navigator based on AsyncStorage, I searched here but always the same result: </p>
  
  <pre><code> const signedIn = async () =&gt; {
      const token = await AsyncStorage.getItem('token');
      if(token) {
        return true;
      } else {
        return false;
      }
    }
  </code></pre>
  
  <p>It always returns true..</p>