Flutter: Unhandled Exception: type 'String' is not a subtype of type 'Map<String, dynamic>'

I am using Firebase and SharePreferences to store some values after authentication. I get this error "Unhandled Exception: type 'String' is not a subtype of type 'Map<String, dynamic>' " I am trying to store 2 Key value pairs as JSON into the sharedPreferences.

Here is my code. User.dart

class GoogleUser {
  final String displayName;
  final String photoUrl;

  GoogleUser(this.displayName, this.photoUrl);
  GoogleUser.fromJson(Map<String, dynamic> json)
      : displayName = json['displayName'],
        photoUrl = json['photoUrl'];
  Map<String, dynamic> toJson() =>
      {'displayName': displayName, 'phototUrl': photoUrl};
}

SharedPref.dart

import 'dart:convert';
import 'package:shared_preferences/shared_preferences.dart';

class SharedPref {
   saveInfo(String key, value) async {
    final prefs = await SharedPreferences.getInstance();
    prefs.setString(key, json.encode(value));
    print("|||||||||||||||||||||||||||||||||||");
    print(value);
  }

  deleteInfo(String key) async {
    final prefs = await SharedPreferences.getInstance();
    prefs.remove(key);
  }
}

This the snippet which I use to save the user data, this is an file named as auth.dart, I get all the values push into sharedpreff.

void storeUserData(displayName, photoUrl) {
  SharedPref sharedPref = SharedPref();
  GoogleUser gUser = new GoogleUser(displayName, photoUrl);
  String user = jsonEncode(gUser);
  sharedPref.saveInfo('googleUser', user);
  print("++++++++++++++++ Shared Prefs ++++++++++++++++++");
  print(user);
}

This is the print output

This is retrieve info code, in a file login.dart

 void getInfo() async {
    final prefs = await SharedPreferences.getInstance();
    print(prefs.getString('googleUser')!);
    Map<String, dynamic> jsonData = jsonDecode(prefs.getString('googleUser')!);
    var userData = GoogleUser.fromJson(jsonData);

    print(
        "--------------->>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>....----------------");
    print(userData.displayName);
    print(userData.photoUrl);
    setState(() {
      //(prefs.getString('googleUser'));
    });
  }

This is the print output for the first print statement in this method, The string appears different compared to how it got stored, and I get error on the line just after the first print statement. I am breaking my head on what is missing here. I referred this article to write this code, https://protocoderspoint.com/store-data-model-object-data-in-sharedpreferences-flutter/

Any help is much appreciated for a newbie Flutter developer