Yeah scapy is nice and there's a lot of nice libs, but security engineering and building of tools Go wins every time. Especially when it's something brand new.
I like Golang a lot and have built a bunch of things in it, but I do not think that for the stuff "Black Hat Go" is talking about that Go is more effective than Python. Python is one of my least favorite language, and it is practically the lingua franca of offensive security (followed by Ruby).
Wouldn't the capability to compile a completely self-contained binary for any platform that can avoid AV be really appealing to pentesters?