The entirety of .NET Core's history is available online. It is one of Microsoft's first completely open frameworks, in that all of the important decisions have been made in the open and the source is completely open. Some of the key Microsoft employees even host a weekly show about it's development.
I decided to take one of my open source projects (OwaspHeaders.Core - https://github.com/GaProgMan/OwaspHeaders.Core) and update the code a little. It had previously used a json for configuration, but after this stream it used the Builder Pattern