[rivo]

When I see these kind of readability-decreasing optimizations in code reviews, I always push back. Almost always, that same Go code queries some other service over the network or loads data from the database, or similar, and nobody will ever notice the speed improvement of IndexOf over Split at the bottom line. But everyone working with that code at a later time will spend extra time (sometimes hours) just trying to understand what's going on. That's much more expensive than a few extra CPU cycles here and there.

Sure, if you're writing an inner loop for some heavy workload, e.g. in graphics or maybe parsing terabytes of JSON, it makes sense. But outside of these rarely occurring situations, you should always prefer readability over low-level optimizations.