code: func isUnreserved(c byte) bool {
  	return (c >= 'a' && c <= 'z') ||
  		(c >= 'A' && c <= 'Z') ||
  		(c >= '0' && c <= '9') ||
  		c == '-' ||
  		c == '_' ||
  		c == '.' ||
  		c == '!' ||
  		c == '~' ||
  		c == '*' ||
  		c == '\'' ||
  		c == '(' ||
  		c == ')'
  }
docs: // isUnreserved return true
  // if the byte c is an unreserved char,
  // as defined in RFC 2396.