linkedlist.go
func (list *LinkedList) PeekFront() (interface{}, bool) {
	list.key.RLock()
	defer list.key.RUnlock()

	if list.first == nil {
		return nil, false
	}
	return list.first.payload, true
}
func (list *LinkedList) PeekFront() (interface{}, bool) {
	list.key.RLock()
	defer list.key.RUnlock()

	if list.first == nil {
		return nil, false
	}
	return list.first.payload, true
}
// PeekFront returns the entry logically stored at the front of this list without removing it.