code: 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
  }
docs: // PeekFront returns the entry logically stored at the front of this list without removing it.