stack.go
func (s *Stack) Peak() (header, data []byte, err error) {
	if s.depth == 0 {
		return nil, nil, nil
	}
	s.guard.Lock()
	defer s.guard.Unlock()
	s.lastAccess = time.Now()
	file, err := s.getFile()
	if err != nil {
		return nil, nil, err
	}
	data = make([]byte, s.currentBlock.DataSize)
	header = make([]byte, s.currentBlock.HeaderSize)
	// Read header
	_, err = file.ReadAt(header, int64(s.currentBlock.HeaderPoint))
	if err != nil {
		return nil, nil, err
	}
	// Read data
	_, err = file.ReadAt(data, int64(s.currentBlock.DataPoint))
	if err != nil {
		return nil, nil, err
	}
	return header, data, nil
}
func (s *Stack) Peak() (header, data []byte, err error) {
	if s.depth == 0 {
		return nil, nil, nil
	}
	s.guard.Lock()
	defer s.guard.Unlock()
	s.lastAccess = time.Now()
	file, err := s.getFile()
	if err != nil {
		return nil, nil, err
	}
	data = make([]byte, s.currentBlock.DataSize)
	header = make([]byte, s.currentBlock.HeaderSize)
	// Read header
	_, err = file.ReadAt(header, int64(s.currentBlock.HeaderPoint))
	if err != nil {
		return nil, nil, err
	}
	// Read data
	_, err = file.ReadAt(data, int64(s.currentBlock.DataPoint))
	if err != nil {
		return nil, nil, err
	}
	return header, data, nil
}
// Peak of stack - get one segment from stack but not remove