How can i used the multi future in FutureBuilder? - flutter

Question

Begins an asynchronous calls the function and multiple.
However, the response to the second call is always null.
I want to update it to the screen when I get all the results.
sometimes invoked Error msg like this :
type 'List' is not a subtype of type 'Map<dynamic, dynamic>'
class _HomePageState extends State<Home> {
final _formKey = GlobalKey<FormState>();
final _formKey2 = GlobalKey<FormState>();
aboutRes about; // delete
var _callStack = [Gateway.Instance.about(), Wifi.Instance.ssidInfo(0)];
#override
void initState() {
super.initState();
}
#override
Widget build(BuildContext context) {
return Scaffold(
body : Padding(
padding: const EdgeInsets.all(15.0),
child: Column(children: [
Expanded(
child: FutureBuilder(
future : Future.wait(_callStack),
key : _formKey,
builder: (context, snapshot) {
if (snapshot.hasError) {
return Text('Invoked Error is ${snapshot.error}');
} else if (snapshot.hasData) {
return ListView (
padding: const EdgeInsets.all(0.8),
children: [
Container(
child : Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
InformationItem(about: snapshot.data[0]),
WirelessItem(ssid: snapshot.data[1]),
],
),
)
]
);
} else {
return CircularProgressIndicator();
}
}
)
),
]),
)
);
}
}
Future<aboutRes> about() async {
aboutRes res;
ApiResponse response = await get(GATEWAY_ABOUT);
// for jsonSerialization
Map resMap = jsonDecode(response.body);
res = aboutRes.fromJson(resMap);
return res;
}