Issue implementing StateNotifierProvider from Riverpod

Question

I am trying to implement a Cart System using Riverpod to manage the state of the Cart.

This is the part where the user clicks on a product to add it to the cart:

   GestureDetector(
                      child: Icon(Icons.shopping_cart),
                      onTap: () async {
                        print("cart test");
                        //create new cart item
                        Cart cartItem = new Cart(
                          id: product.id,
                          name: product.name,
                          oldPrice: product.oldPrice,
                          price: product.price,
                          imageUrl: product.imageUrl,
                          category: product.category,
                          quantity: 1
                        );
                        var cartInstance = context.read(cartListProvider);
                        if(isExistsInCart(cartInstance.state,cartItem))
                          context.read(cartListProvider).edit(cartItem,1);
                        else
                          {
                            context.read(cartListProvider).add(cartItem);//if already available in cart, just increase quantity
                            var string = json.encode(context.read(cartListProvider).state);
                            await storage.write(key: cartKey, value: string);
                            
                          }




                      },
                    )

Here you have the provider class:

import 'package:cart_system_riverpod/models/cart.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

final cartListProvider = StateNotifierProvider((ref){

  return CartList([]); //init empty cart

});

I have also added ProviderScope to the top of the Widgets tree.

My issue is that I am getting errors implementing:

cartInstance = context.read(cartListProvider)

and

context.read(cartListProvider).edit(cartItem,1);

always at the read(...) part

The editor shows the hint The method 'read' isn't defined for the type 'BuildContext'.