errors.go
func (list ErrorList) Last() error {
	if len(list) == 0 {
		return nil
	}
	return list[len(list)-1]
}
func (list ErrorList) Last() error {
	if len(list) == 0 {
		return nil
	}
	return list[len(list)-1]
}
// Last returns the last error in the list or nil.
// Can be called for a nil ErrorList.