code: func (s *Scanner) SeekFromStart(offset int64) (previous int64, err error) {
  	// if seeking we assume that you are not interested in the header
  	if s.version == 0 {
  		s.version = VersionSupported
  	}
  
  	previous, err = s.r.Seek(0, io.SeekCurrent)
  	if err != nil {
  		return -1, err
  	}
  
  	_, err = s.r.Seek(offset, io.SeekStart)
  	return previous, err
  }
docs: // SeekFromStart sets a new offset from start, returns the old position before
  // the change.