In standard go you would not implement Is but would use the errors.Is call. How would this work if it is a sentinel error as you would use with errors.Is??
> An error is considered to match a target if it is equal to that target or if it implements a method Is(error) bool such that Is(target) returns true.
by default errors.Is matches the exact error variable, but you can use it to match other errors as well.
I stand corrected. Still you cannot implement an Is on a sentinel error and is only applicable to concrete error types. And if I'm using concrete types I'm going to us errors.As
