Error: The method 'showSnackBar' isn't defined for the class 'ScaffoldState

[jianboy]

lib/controllers/auth/auth_provider.dart:53:34: Error: The method 'showSnackBar' isn't defined for the class 'ScaffoldState'.
 - 'ScaffoldState' is from 'package:flutter/src/material/scaffold.dart' ('/opt/flutter/packages/flutter/lib/src/material/scaffold.dart').
Try correcting the name to the name of an existing method, or defining a method named 'showSnackBar'.
            Scaffold.of(context).showSnackBar((SnackBarWidget.MainSnackBarError(
                                 ^^^^^^^^^^^^
lib/controllers/auth/auth_provider.dart:77:20: Error: The method 'showSnackBar' isn't defined for the class 'ScaffoldState'.
 - 'ScaffoldState' is from 'package:flutter/src/material/scaffold.dart' ('/opt/flutter/packages/flutter/lib/src/material/scaffold.dart').
Try correcting the name to the name of an existing method, or defining a method named 'showSnackBar'.
                  .showSnackBar((SnackBarWidget.MainSnackBarSuccess(
                   ^^^^^^^^^^^^
lib/controllers/auth/auth_provider.dart:86:36: Error: The method 'showSnackBar' isn't defined for the class 'ScaffoldState'.
 - 'ScaffoldState' is from 'package:flutter/src/material/scaffold.dart' ('/opt/flutter/packages/flutter/lib/src/material/scaffold.dart').
Try correcting the name to the name of an existing method, or defining a method named 'showSnackBar'.
              Scaffold.of(context).showSnackBar(
                                   ^^^^^^^^^^^^
lib/controllers/auth/auth_provider.dart:94:32: Error: The method 'showSnackBar' isn't defined for the class 'ScaffoldState'.
 - 'ScaffoldState' is from 'package:flutter/src/material/scaffold.dart' ('/opt/flutter/packages/flutter/lib/src/material/scaffold.dart').
Try correcting the name to the name of an existing method, or defining a method named 'showSnackBar'.
          Scaffold.of(context).showSnackBar((SnackBarWidget.MainSnackBarError(
                               ^^^^^^^^^^^^
lib/controllers/auth/auth_provider.dart:100:32: Error: The method 'showSnackBar' isn't defined for the class 'ScaffoldState'.
 - 'ScaffoldState' is from 'package:flutter/src/material/scaffold.dart' ('/opt/flutter/packages/flutter/lib/src/material/scaffold.dart').
Try correcting the name to the name of an existing method, or defining a method named 'showSnackBar'.
          Scaffold.of(context).showSnackBar(
                               ^^^^^^^^^^^^
lib/controllers/auth/auth_provider.dart:129:20: Error: The method 'showSnackBar' isn't defined for the class 'ScaffoldState'.
 - 'ScaffoldState' is from 'package:flutter/src/material/scaffold.dart' ('/opt/flutter/packages/flutter/lib/src/material/scaffold.dart').
Try correcting the name to the name of an existing method, or defining a method named 'showSnackBar'.
                  .showSnackBar((SnackBarWidget.MainSnackBarSuccess(
                   ^^^^^^^^^^^^
lib/controllers/auth/auth_provider.dart:138:32: Error: The method 'showSnackBar' isn't defined for the class 'ScaffoldState'.
 - 'ScaffoldState' is from 'package:flutter/src/material/scaffold.dart' ('/opt/flutter/packages/flutter/lib/src/material/scaffold.dart').
Try correcting the name to the name of an existing method, or defining a method named 'showSnackBar'.
          Scaffold.of(context).showSnackBar(
                               ^^^^^^^^^^^^
lib/controllers/auth/auth_provider.dart:142:32: Error: The method 'showSnackBar' isn't defined for the class 'ScaffoldState'.
 - 'ScaffoldState' is from 'package:flutter/src/material/scaffold.dart' ('/opt/flutter/packages/flutter/lib/src/material/scaffold.dart').
Try correcting the name to the name of an existing method, or defining a method named 'showSnackBar'.
          Scaffold.of(context).showSnackBar(
                               ^^^^^^^^^^^^
lib/controllers/main/user_provider.dart:99:34: Error: The method 'showSnackBar' isn't defined for the class 'ScaffoldState'.
 - 'ScaffoldState' is from 'package:flutter/src/material/scaffold.dart' ('/opt/flutter/packages/flutter/lib/src/material/scaffold.dart').
Try correcting the name to the name of an existing method, or defining a method named 'showSnackBar'.
            Scaffold.of(context).showSnackBar(
                                 ^^^^^^^^^^^^
lib/controllers/main/user_provider.dart:141:34: Error: The method 'showSnackBar' isn't defined for the class 'ScaffoldState'.
 - 'ScaffoldState' is from 'package:flutter/src/material/scaffold.dart' ('/opt/flutter/packages/flutter/lib/src/material/scaffold.dart').
Try correcting the name to the name of an existing method, or defining a method named 'showSnackBar'.
            Scaffold.of(context).showSnackBar(
                                 ^^^^^^^^^^^^
lib/controllers/main/user_provider.dart:162:34: Error: The method 'showSnackBar' isn't defined for the class 'ScaffoldState'.
 - 'ScaffoldState' is from 'package:flutter/src/material/scaffold.dart' ('/opt/flutter/packages/flutter/lib/src/material/scaffold.dart').
Try correcting the name to the name of an existing method, or defining a method named 'showSnackBar'.
            Scaffold.of(context).showSnackBar(
                                 ^^^^^^^^^^^^
Target kernel_snapshot failed: Exception