user/user.go
func AddSystemUser(name, homeDir string, gid int) (uid int, err error) {
	s := NewShadow(name)
	if err = s.Add(nil); err != nil {
		return
	}

	return NewSystemUser(name, homeDir, gid).Add()
}
func AddSystemUser(name, homeDir string, gid int) (uid int, err error) {
	s := NewShadow(name)
	if err = s.Add(nil); err != nil {
		return
	}

	return NewSystemUser(name, homeDir, gid).Add()
}
// AddSystemUser adds a system user to both user and shadow files.