GitHub repo is now a normal part of tech books.
I expect Jupyther notebooks will be too, in "a few" years...
Manning | ASP.NET Core in Action
andrewlock/asp-dot-net-core-in-action: Source code examples for ASP.NET Core in Action
Manning | .NET Core in Action
dmetzgar/dotnetcoreinaction: Companion code from .NET Core in Action by Manning Publishing
Hanselminutes Technology Podcast - Fresh Air and Fresh Perspectives for Developers - ASP.NET Core in Action with Andrew Lock
Project Jupyter | JupyterHub