How can I add request header automatically using http package - flutter

Question

Currently I'm sending header with every request like as follow which is very repetitive.
Is there any process so that all my request will have a request header automatically ?
Or how can I avoid code repetition for the following lines:
SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
String token = sharedPreferences.getString('accessToken');
headers: {
'Contet-type': 'application/json',
'Authorization': 'Bearer $token',
}
My complete API Request code:
Future<http.Response> getAUser(userId) async {
SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
String token = sharedPreferences.getString('accessToken');
return await http.get(
'$baseUrl/user/$userId/',
headers: {
'Contet-type': 'application/json',
'Authorization': 'Bearer $token',
},
).timeout(Duration(seconds: 30));
}

Answer 1

Yes you can centralize the headers in a separate class!
class BaseService {
Map<String, String> baseHeaders;
Future initBaseService() async {
final preferences = await SharedPreferences.getInstance();
baseHeaders= {
"Accept": "application/json",
"Content-Type": "application/json; charset=utf-8",
"Authorization": "Bearer ${preferences.getString("TOKEN")}",
};
}
}
And then, you can inherit your class with the base class to have access to these methods.
class UserService extends BaseService {
Future<http.Response> getAUser(userId) async {
await initBaseService();
return await http
.get(
'$baseUrl/user/$userId/',
headers: baseHeaders,
)
.timeout(Duration(seconds: 30));
}
}