find the index of a selected item in flutter web
getDropDownMenuItems(snapshot) {
Map<int, dynamic> mapWithIndex = snapshot.data.services.asMap;
List<DropdownMenuItem> _items = [];
mapWithIndex.forEach((index, item) {
_items.add(
DropdownMenuItem<int>(
value: index,
child: Text(item.service),
),
);
});
return _items;
}