How to properly "refresh" Widgets inside FutureBuilder()

Question

I have a Listview.builder() inside a FutureBuilder() that displays data fetched from API. I can retrieve the data successfully. But when I call the refreshData() function, previous data gets appended in the list.. How do I properly 'refresh' the widgets inside a FutureBuilder()?

Note: I'm only using get request here, so it's impossible that the data gets duplicated in the back-end. So the problem actually lies in displaying the data.

Here is my code:

class _MyHomePageState extends State<MyHomePage> {
  List<Giver> _givers = [];
  Future giversList;

  getData() async {
    _givers.addAll(await NetworkHelper().fetchGivers());
    return _givers;
  }

  refreshData() {
    giversList = getData();
  }

  @override
  void initState() {
    super.initState();
    giversList = getData();
  }

  @override
   Widget build(BuildContext context) {
     return Scaffold(
       body: SafeArea(
       child: Column(
         children: <Widget>[
            RaisedButton(
              onPressed: (){
                setState(() {
                refreshData();
              });
            },
          child: Text('Refresh'),
        ),
        FutureBuilder(
          future: giversList,
          builder: (context, snapShot){
            switch(snapShot.connectionState) {
              case ConnectionState.none:
                return Center(child: Text('none'));

              case ConnectionState.active:

              case ConnectionState.waiting:
                return Center(child: CircularProgressIndicator());

              //this is where the listview is created
              case ConnectionState.done:
                return ListView.builder(
                  shrinkWrap: true,
                  itemCount: _givers.length,
                  itemBuilder: (context, index) {
                    return ListTile(
                      title: Text(snapShot.data[index].name),
                      subtitle: Text(snapShot.data[index].address),
                    );
                  });

                  default:
                   return Center(child: Text('Default!'));
                 }
               },
             )
           ],
         ),
       ),
     );
   }
}

Answer 1

As @pskink mentioned in the comment above, I just replaced _givers.addAll(await NetworkHelper().fetchGivers()); with _givers = await NetworkHelper().fetchGivers();

Thanks for the help!