I wanted to use something like a right-hand wall solver, but the fact that you don't know the maze ahead of time and you can't see what something is without trying to move into it made that difficult. This semi-brute-force approach works well enough. I originally stopped as soon as I found the oxygen system and figured out the shortest path, but once I submitted that answer and saw that part 2 wanted the full map explored, I figured I might as well just fill the map all at once.
I think I would have been stuck on part 1 longer if my input set didn't happen to find the goal system fairly easily (or maybe my debug drawing helped me work through it with that input set specifically, I'm not sure) since a different input set required some tweaking to the max-visited threshold in order to find things that my first input set found with a lower setting.
Regardless, I'm pretty excited that I came to Trémaux's algorithm, more or less, on my own. I went to Wikipedia to see if I was on the right track and lo and behold, I had come to a version of it myself.
Part 2 turned out easier than I originally thought. I suspected this solution would work, but wasn't completely confident. It can only work for the type of maze used by this problem (where there are no loops of open areas). I'm just glad I didn't need A* or anything.
Oh, and this `stringer` command that allows debug printing of enums can be installed with `go install golang.org/x/tools/cmd/stringer@latest`
I will probably end up regretting this since I assume the "wait to be given an input from some other process before continuing execution" paradigm is going to come up again, but this part 2 goroutine+channel solution felt good (taking advantage of Go features) and made me happy, so I rolled with it.
