There is a third option, secret door number three, and that is go to the Go language track repository on GitHub and watch it. Then when issues come in, help respond when pull requests come in, help review them. That would be an immense help to keep the language going and the people happy. So that’s this sort of secret path to maintainership route.
The other pieces that you’ve already mentioned – doing the exercises, submitting them to the website… Once you submit, you get access to all of the other solutions to that particular exercise, so you can browse around and look at what other people have done, how that’s different from yours; you can learn from reading their code and you can learn from comments that other people give on these solutions.
I have a little bot that does some linting and a little bit of static analysis in Go, to give feedback. It’s mostly stuff that I was giving feedback on over and over again, so I just added this to the bot so that it automates that a little bit. But yeah, do the exercise and get feedback. In order to give feedback on an exercise, I would encourage you to do the exercise first, just to get a little bit of a feel for what the problem is and the different types of issues that people might run into with it.