code: func (s *Random) Read(b []byte) (n int, err error) {
  	s.mutex.Lock()
  	defer s.mutex.Unlock()
  
  	for i, _ := range b {
  		b[i] = s.readByte()
  	}
  
  	return len(b), nil
  }
docs: // Read fills specified byte array with random data.
  // Always return parameter array length and no errors.