code: func (f RuneMatcherFunc) Match(str string) (offset int, matchStr string) {
  	offset = -1
  	length := len(str)
  	if length == 0 {
  		return
  	}
  
  	for i, r := range str {
  		if f(r) {
  			continue
  		}
  		if i != 0 {
  			offset = i
  			matchStr = str[:i]
  			return
  		}
  		return
  	}
  
  	offset = length
  	matchStr = str
  	return
  }
docs: // Match processes the given string until it encounters a rune that doesn't
  // match.