code: func (l *Scanner) Peek2() (a, b byte) {
  	if l.pos == len(l.data) {
  		return 0, 0
  	}
  	if l.pos+1 == len(l.data) {
  		return l.data[l.pos], 0
  	}
  	return l.data[l.pos], l.data[l.pos+1]
  }
docs: // Peek2 reads two first bytes at current position without advancing it.
  // If there not enough data it returs 0.