So beside familiarizing the language syntax, I need to be aware of a set of unofficial tools and plugins, which are likely going to change in the next couple months, to be able to read the code.
It's an official tool. Also, most interfaces are very small (one to two methods) so it's pretty easy to figure out. I read/write a decent amount of Go every day and it's not often that I'm asking myself "what implements this interface?".
"go oracle" is right there with "go build" etc, an official tool that shouldn't change any more than the other tools that's part of the Go distribution.