archive.go
func New(file *os.File) Archive {
	if filepath.Ext(file.Name()) == ".zip" {
		return zip.New(file)
	}
	return tar.New(file)
}
func New(file *os.File) Archive {
	if filepath.Ext(file.Name()) == ".zip" {
		return zip.New(file)
	}
	return tar.New(file)
}
// New archive
// If the exentions of the target file is .zip, the archive will be in the zip
// format, otherwise, it will be a tar.gz archive.