title: Can't retrieve a number of document into firestore flutter
body: <p>I have a small problem, I need to retrieve into my list a collection retrieved by StreamBuilder from Firestore.
  I am using <code>snapshot.data.documents.lenght </code> but once I add it I got error:</p>
  <pre><code>Class 'DocumentSnapshot' has no instance getter 'documents'.
  Receiver: Instance of 'DocumentSnapshot'
  Tried calling: documents
  </code></pre>
  <p>this is my code:</p>
  <pre><code>  Stream&lt;DocumentSnapshot&gt; getDatabase() async* {
      FirebaseUser user = await FirebaseAuth.instance.currentUser();
      yield* Firestore.instance
          .collection('dataCollection')
          .document(user.uid)
          .snapshots();
    }
  
    @override
    Widget build(BuildContext context,) {
      return StreamBuilder(
        stream: getDatabase(),
        builder: (context, snapshot,) {
          if (snapshot.data != null) {
            return Column(
              children: &lt;Widget&gt;[
                Container(
                  height: 500,
                  child: ListView.builder(
                    shrinkWrap: true,
                    itemCount: 2,
                    itemBuilder: (BuildContext context, int index) {
                      return Card(
                        color: Color(0xFF1f2032),
                        elevation: 15,
                        child: Text(
                          snapshot.data['phone']..
                          
  </code></pre>