i grew up a long time before stack overflow. actually used man pages and read books. there is just _no way_ to program in Rust or Go without access to a search engine and the package libraries.
I've done various rust and clojure projects by downloading a lot of git repos ahead of time for reference while on a long-haul flight. This works pretty well, but you need to do a bit of research ahead of time on which libraries you might want access to. This is probably slower, as you have to read source code and think more about the type signatures (rather than looking at some misc example), but if you have 15 hours, what else are you going to do?
You can spin up godoc locally and access it locally fyi. Wont help pull in a new package. And you can always drill down into the stdlib implementation right from your editor if you have jump to declaration. I wrote a custom consensus protocol implementation in Go on a flight for work sans wifi.