add_client.dart

import 'package:dio/dio.dart';


final Dio client = Dio();

client.interceptors.add(kDebugMode
        ? LogInterceptor(
      request: true,
      responseBody: true,
      requestHeader: true,
      error: true,
      requestBody: true,
      responseHeader: true,
    )
        : LogInterceptor(
      request: false,
      responseBody: false,
      requestHeader: false,
      error: false,
      requestBody: false,
      responseHeader: false,
    ));

    client.interceptors.add(TokenInterceptor(userSession));

token_interceptor.dart

import 'package:dio/dio.dart';
import 'package:janstore/src/config/session.dart';

class TokenInterceptor extends Interceptor {
  final UserSession userSession;

  TokenInterceptor(this.userSession);

  @override
  onRequest(RequestOptions options,RequestInterceptorHandler handler) async {
    if (await userSession.hasToken()) {
      var token = await userSession.token();
      if (token != null && token.isNotEmpty) {
        options.headers['authorization'] = 'Bearer $token';
        print("token found. ");
      }
    } else {
      print("token not found,ignored. probably a guest.");
    }
    return super.onRequest(options, handler);
  }
}

user_session.dart

const TOKEN_KEY = "token";

class UserSession {

    GetStorage box=GetStorage();
  
  
  /// this  function check if user has access token */
  bool hasToken() {
    return box.read(tokenKey) != null ? true : false;
  }

  /// this  function retrieve user  access token */
  String? token() {
    return box.read(tokenKey);
  }

  logout() {
    box.remove(tokenKey);
  }

}