title: Cant match users in firebase
body: <p>I can't randomly get user from firebase</p>
  <p>I'm doing dating app with react native and firebase.</p>
  <p>Users can log in with google and set their accounts, but I can't match users.</p>
  <p>I can pick 1 user but cant display user's data.</p>
  <p>I tried:</p>
  <ul>
  <li>i tried get all users from firebase realtime database</li>
  <li>i can pick 1 user and log user's details but cant display in app</li>
  </ul>
  <p>And sometimes <code>user.uid</code> returns null even if i logged in.</p>
  <pre><code>function getRandomUser() {
    const numberOfUsers = 15;
    const randomIndex = Math.floor(Math.random() * numberOfUsers);
    var ref = firebase.database().ref(&quot;/users/&quot;);
  
    ref
      .limitToFirst(1)
      .once(&quot;value&quot;)
      .then((snapshot) =&gt; {
        var randomUser = snapshot.val();      
        console.log(randomUser);
        console.log(randomUser.bio);//this is not even display in console
      });
  }
  </code></pre>