i need help

[EwigLife]

class _SignUpPageState extends State<SignUpPage> {
  final TextEditingController fnameController = TextEditingController();
  final TextEditingController lnameController = TextEditingController();
  final TextEditingController passwrodController = TextEditingController();
  final TextEditingController emailController = TextEditingController();

  ShopifyAuth auth = ShopifyAuth.instance;
  ShopifyUser user;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            TextFormField(
              controller: emailController,
            ),
            TextFormField(
              controller: passwrodController,
            ),
            ElevatedButton(
                onPressed: () async {
                  await auth.createUserWithEmailAndPassword(
                      email: emailController.text,
                      password: passwrodController.text);
                  print(emailController.text + passwrodController.text);
                },
                child: Text('Sign up'))
          ],
        ),
      ),
    );
  }
}

E/flutter ( 1821): Receiver: null
E/flutter ( 1821): Tried calling:
E/flutter ( 1821): #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:54:5)
E/flutter ( 1821): #1 ShopifyUser.fromJson
package:flutter_simple_shopify/…/src/shopify_user.dart:30
E/flutter ( 1821): #2 ShopifyAuth.createUserWithEmailAndPassword
package:flutter_simple_shopify/…/src/shopify_auth.dart:46
E/flutter ( 1821):
E/flutter ( 1821): #3 _SignUpPageState.build.
package:e_com_app_v_1_0/Screens/SignupPage.dart:35
E/flutter ( 1821):
E/flutter ( 1821):

i am geting the above response when trying to sign in please guide where i am wrong