title: Dart Error: Unhandled exception: E/flutter ( 5079): Invalid argument: Instance of 'Future<String>'
body: <p>I am trying to add document to my cloud firestore DB. In this manner.</p>
  
  <pre><code>Future&lt;String&gt; currentlyIn()async{
       FirebaseAuth auth = FirebaseAuth.instance;
      String fuser = await auth.currentUser();
      });
       return fuser.uid;
     }
  
  
  Map&lt;String, dynamic&gt; votedown() {
      Map&lt;String, dynamic&gt; comdata = &lt;String, dynamic&gt;{
        'user_Id':currentlyIn(),
        'actual_vote':0,
        'voteUp': false,
  
      };
      return comdata;
    }
  
  DocumentReference storeReference =Firestore.instance.collection('htOne').document('docq');
    await storeReference.setData(votedown());
  </code></pre>
  
  <p>However I get this error anytime I run the code. I need help on how to go about this successfully</p>
  
  <pre><code>E/flutter ( 6263): [ERROR:flutter/shell/common/shell.cc(181)] Dart Error: Unhandled exception: 
  E/flutter ( 6263): Invalid argument: Instance of 'Future&lt;String&gt;'
  E/flutter ( 6263): #0      StandardMessageCodec.writeValue (package:flutter/src/services/message_codecs.dart:353:7) 
  E/flutter ( 6263): #1      FirestoreMessageCodec.writeValue (file:///C:/NoFlutterPerms/Git/flutter/.pub-cache/hosted/pub.dartlang.org/cloud_firestore-0.7.4/lib/src/firestore_message_codec.dart:38:13)
  </code></pre>