title: Using GeoFire queries in Swift does not give useful output
body: <p>I'm pretty desperate right now because I'm trying to use GeoFire on my Firebase Database to find nearby users.
  I'm pretty much stuck for two days now.
  I searched Google and stackoverflow a lot and tried everything I found there but without any success. Now my last hope is to create this thread myself and hope someone can help me.</p>
  
  <p>My database pretty much looks like this:</p>
  
  <pre><code>users
      user_id1
          email: xxx@gmail.com
          username: xxx
      user_id2
          email: yyy@gmail.com
          username: yyy
  users_locations
      user_id1
          location
              g: xxxx
              l
                  0: 30.0000
                  1: 5.0000
      user_id2
          location
              g: yyyy
              l
                  0: 30.0010
                  1: 5.0010
  </code></pre>
  
  <p>I don't know if it is necessary to save the location data seperated from the users but I also tried to save it like this with the same results so I think it doesn't matter:</p>
  
  <pre><code>users
      user_id1
          email: xxx@gmail.com
          username: xxx
          location
              g: xxx
              l
                  0: 30.0000
                  1: 5.0000
  </code></pre>
  
  <p>Now the code I'm using:</p>
  
  <p>To write the location into the database I use the following, which is working fine:</p>
  
  <pre><code>let user = FIRAuth.auth()?.currentUser
  let uid = user?.uid
  
  let ref = FIRDatabase.database().reference()
  let geofireRef = ref.child("users_locations")
  let geoFire = GeoFire(firebaseRef: geofireRef.child(uid!))
  
  geoFire?.setLocation(myLocation, forKey: "location")
  </code></pre>
  
  <p>Now I try to use a GeoFire Query to show me all users in a defined radius which is printing nothing for this one:</p>
  
  <pre><code>let ref = FIRDatabase.database().reference()
  let geofireRef = ref.child("users_location")
  let geoFire = GeoFire(firebaseRef: geofireRef)
  
  let circleQuery = geoFire?.query(at: center, withRadius: 10)
  circleQuery?.observe(.keyEntered, with: { (key: String?, location: CLLocation?) in
           print("Key '\(key!)' entered the search are and is at location '\(location!)'")
      })
  </code></pre>
  
  <p>I figured out that I get a result if I go to my actual uid child. Then it print my actual users location and key but that's of course not what I want to have.</p>
  
  <pre><code>let geoFire = GeoFire(firebaseRef: geofireRef.child(uid!))
  </code></pre>
  
  <p>So I want GeoFire to search through my uid's in 'users_locations' and return me all uid's which are in my defined radius.</p>
  
  <p>To me, it seems like it is only searching for the child named 'location' in the child defined in my Reference (users_location -> user_uid) and if I try to query over 'users_location', I get nothing.</p>
  
  <p>What am I doing wrong?
  How can I make the query search reference child and give me the uid back?</p>