Ok I have been running code through the new fork and had to do a bit of a cleanup of the context interface. I like having the context separated out because it means you can call the RoundTripper function directly and it cleans up many of the routines. From a performance side however, I was concerned about having broken out the different pieces of the context into separate context elements stored on the request. This means that the system would have to search through multiple. Instead I went back to the structure you had but put it on the Context. I've got several of the examples running now and submitted a merge request back to your fork. Feel free to make any suggestions.
I'm working on the making more of the examples - particularly the HTTPDUMP one.