adding token with the url string concatenation - flutter

Question

hi I want to send token with my api url i tried it by concatenate the token with api url but not. it's showing the error you cannot call the value on null. i cannot figure it out. any help from your side should be appreciate.
This is my api code:
class APIService {
String baseurl = "https://b2all.live/api";
var log = Logger();
FlutterSecureStorage storage = FlutterSecureStorage();
//old get
Future get(String url) async {
await storage.read(key: "api_token");
url = formater(url);
// /user/register
var response = await http.get(
url,
);
if (response.statusCode == 200) {
log.i(response.body);
return json.decode(response.body);
}
log.i(response.body);
log.i(response.statusCode);
}
String formater (String url) {
return baseurl+url;
}
}
And this is my fetching data from api code:
#override
void initState() {
super.initState();
fetchData();
}
void fetchData() async {
var preferences = await SharedPreferences.getInstance();
String api_token = preferences.getString('api_token');
print(api_token);
var response = await networkHandler.get(
"/profile/DvIXUN1CAgYMQzKri0dx3XVxfcABDjbPEg1QyHVD4vu1pQM8pRF56OjLgVW8");
setState(() {
profileModelFix = ProfileModelFix.fromJson(response);
circular = false;
});
}
this is my model file. it's showing error on model. but i cannot figure it out. any help from your side will be helpful for me.
import 'package:flutter/foundation.dart';
import 'package:json_annotation/json_annotation.dart';
part 'profileModelFix.g.dart';
#JsonSerializable()
class ProfileModelFix {
String name;
String user_name;
String dob;
String phone;
String gender;
String bio;
String api_token;
ProfileModelFix ({
this.name, this.user_name, this.dob, this.phone, this.gender, this.bio, this.api_token,
});
factory ProfileModelFix.fromJson(Map<String,dynamic> json) =>
_$ProfileModelFixFromJson(json);
Map<String,dynamic> toJson() => _$ProfileModelFixToJson(this);
}