I hope you realize that this won’t even compile.

The err in your if is a newly allocated variable by :=, different than the err allocated by the x prototype, and you’d also return a nil error even if impl returned an error.

The Go compiler is smart enough to prevent you from doing this beginner mistake:

result parameter err not in scope at return. inner declaration of var err error.

https://go.dev/play/p/VdWVOL51wZf

You would have to first declare thing prior to the if statement, then replace := by = .. the beauty of adding verbosity and longer-lived variables for the sake of trying to write return instead of return err in Go.