func IsMatchError(err error) bool {
	_, ok := err.(MatchError)
	return ok
}
IsMatchError returns true if err is a MatchError,
false otherwise.
package errz
type MatchError struct {
	reason string
}
func (m MatchError) Error() string {
	return m.reason
}
func NewMatchError(reason string) MatchError {
	return MatchError{reason}
}