func (l *List) Get(pos uint) (interface{}, bool) {
	l.key.RLock()
	defer l.key.RUnlock()

	if pos > uint(len(l.underlyer)) {
		return nil, false
	}
	return l.underlyer[pos], true
}
func (l *List) Get(pos uint) (interface{}, bool) {
	l.key.RLock()
	defer l.key.RUnlock()

	if pos > uint(len(l.underlyer)) {
		return nil, false
	}
	return l.underlyer[pos], true
}
// Get retreives the value stored in a particular position of the list.
// If no item exists at the given position, the second parameter will be
// returned as false.