Hi, I’m so sorry for replying after months, but I haven’t looked at Medium for a while, I hope that this comment will help you or any reader out there.

You should think about why you’re using ProductService in SharedModule, it doesn’t feel right to me :P You should be asking yourself: whose is the ProductService useful for? If it’s all the app, then it belongs to Core (or another module imported by AppModule, let’s say ApiModule). If it’s only ProductsModule, then it goes there. If it has meaning only with some shared component (ex. ProductsComponent), then it may go in SharedModule.