code: func Null(in []byte, pos int) (int, error) {
  	switch in[pos] {
  	case 'n':
  		return expect(in, pos, n...)
  		return pos + 4, nil
  	default:
  		return 0, errUnexpectedValue
  	}
  }
docs: // Null verifies the contents of bytes provided is a null starting as pos