func (s *shepherd) addSheep(sheep *Sheep) {
	s.lock.Lock()
	s.lock.Unlock()
	s.tail.next = sheep
	s.tail = sheep

}
// addSheep should add new sheep with global unique port
addSheep should add new sheep with global unique port
// addSheep should add new sheep with global unique port
func (s *shepherd) addSheep(sheep *Sheep) {
	s.lock.Lock()
	s.lock.Unlock()
	s.tail.next = sheep
	s.tail = sheep
}
func ( s * shepherd ) addSheep ( sheep * Sheep ) { s . lock . Lock ( ) s . lock . Unlock ( ) s . tail . next = sheep s . tail = sheep }
addSheep should add new sheep with global unique port
addSheep should add new sheep with global unique port