func (opt byKeyOption) apply(o *lookupOptions) error {
	if o.key != nil {
		return ErrDuplicateOption
	}
	o.key = &opt.Key
	return nil
}
// apply simply applies the option.
apply simply applies the option.
// apply simply applies the option .
func (opt byKeyOption) apply(o *lookupOptions) error {
	if o.key != nil {
		return ErrDuplicateOption
	}
	o.key = &opt.Key
	return nil
}
func ( opt byKeyOption ) apply ( o * lookupOptions ) error { if o . key != nil { return ErrDuplicateOption } o . key = & opt . Key return nil }
apply simply applies the option.
apply simply applies the option .