"_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'List<dynamic>'"

{"78":{"id":118,"first_name":"test","last_name":null,"email":"jignesh.test@gmail.com","phone":"","city":"null","state":"null","countrie_id":1,"location":"null","lat":"37.421998333333335","lng":"-122.08400000000002","image":"","role_id":3,"client_id":3,"coordinator_id":1,"sst_id":2,"created_at":"2018-10-08 10:59:18","updated_at":"2018-10-08 10:59:18","deleted_at":null,"status":0},
"79":{"id":119,"first_name":"Rahul test","last_name":null,"email":"rahul.test@gmail.com","phone":"","city":"null","state":"null","countrie_id":1,"location":"null","lat":"19.2284","lng":"72.85813","image":"","role_id":3,"client_id":3,"coordinator_id":1,"sst_id":2,"created_at":"2018-10-08 11:19:14","updated_at":"2018-10-08 11:19:14","deleted_at":null,"status":0},
"80":{"id":120,"first_name":"Customer Name","last_name":null,"email":"jjkkk@gmail.com","phone":"","city":"Mumbai","state":"Maharastra","countrie_id":1,"location":"virar","lat":"123","lng":"456","image":"images/customer_image/0hUSFUSqYAQTt57bVnnHjuQUOACECWzBOfJLWWa6.png","role_id":3,"client_id":1,"coordinator_id":1,"sst_id":2,"created_at":"2018-10-09 12:24:08","updated_at":"2018-10-09 14:03:07","deleted_at":null,"status":0},"status":"success","message":"List Fetched Successfully."}

Future<PosModelData> posList(){
  print('pos list api called');
  return networkUtil.post("http://192.168.0.46/api/v1/poslist",body:{
      "sstId":"2"
  }).then((response){
    if(response["status"]=="success"){
      print("List fetched");
      posLists=((response) as List).map((data)=>new PosModelData.fromJson(data)).toList();
      // print(response.toString());
      // print(posLists);
    }
  });
}

class PosModelData {
  final String first_name;
  final String last_name;
  final String email;

  PosModelData({this.first_name, this.last_name, this.email});

  factory PosModelData.fromJson(Map json) {
    return new PosModelData(
      first_name: json['first_name'],
      last_name: json['last_name'],
      email: json['email'],
    );
  }
}