If the user can do anything with the error, then it is idiomatic to return a discrete, comparable error variable var ErrTryAgain = errors.New("...") or an

If the user can do anything with the error, then it is idiomatic to return a discrete, comparable error variable var ErrTryAgain = errors.New("...") or an error type with additional contextual information type RetryError struct { ... } These are both opt-in; if your users have no need to differentiate or act on errors, fmt.Errorf("...") is totally sufficient. You're acting as if this is some critical flaw in the language. It's nothing like that.