We have a lot of Go services in production and errors have never been a performance issue. In the happy path, when there're no errors, errors are basically no-op. We don't use errors for control flow, though; only for exceptional situations, which aren't triggered often. If we want to branch based on an error, we use errors.Is. I don't remember ever having to inspect an error's string, that sounds like a hack. Usually, branching on an error's type is a rare scenario, even if it uses reflection, you usually just bubble up the error. In practice, at runtime, Go's error handling is just a bunch of TEST RAX, RAX instructions. Do you have benchmarks to show otherwise?
