func LookupGroup(groupname string) (Group, error) {
	return lookupGroup(groupname)
}
LookupGroup looks up a group by its name in /etc/group. If the group cannot
be found (or there is no /etc/group file on the filesystem), then LookupGroup
returns an error.
package user
import (
	"errors"
)
var (
	ErrUnsupported = errors.New("user lookup: operating system does not provide passwd-formatted data")
	ErrNoPasswdEntries = errors.New("no matching entries in passwd file")
	ErrNoGroupEntries  = errors.New("no matching entries in group file")
)
func LookupUser(username string) (User, error) {
	return lookupUser(username)
}
func LookupUid(uid int) (User, error) {
	return lookupUid(uid)
}