Infinite recursive call

A function that calls itself recursively needs to have an exit
condition. Otherwise it will recurse forever, until the system runs
out of memory.

This issue can be caused by simple bugs such as forgetting adding an
exit condition. It can also happen "on purpose". Some languages have
[tail call optimization](https://en.wikipedia.org/wiki/Tail_call)
which makes certain infinite recursive calls safe to use. Go, however,
does not implement TCO, and as such a loop should be used instead.

