code: func (l *waiterList) PushFront(e *Entry) {
  	waiterElementMapper{}.linkerFor(e).SetNext(l.head)
  	waiterElementMapper{}.linkerFor(e).SetPrev(nil)
  
  	if l.head != nil {
  		waiterElementMapper{}.linkerFor(l.head).SetPrev(e)
  	} else {
  		l.tail = e
  	}
  
  	l.head = e
  }
docs: // PushFront inserts the element e at the front of list l.