Expose Errors as public

[jerome-laforge]

I need to do some check according error returns Apply.
Unfortunately errors are private.
Is It possible to expose them as public errors?

That replace this:

if err.Error() == "key not found" {
   // manage key not found
}

by

if errors.Is(err, scanner.ErrKeyNotFound) {
    // manage key not found
}

I can make PR, if it is ok for you.

Thanks

[jerome-laforge]

Hello @savaki
any news about this issue?

Thanks for your support