code: func ValidatePattern(ch *Changeset, field string, pattern string, opts ...Option) {
  	val, exist := ch.changes[field]
  	if !exist {
  		return
  	}
  
  	options := Options{
  		message: ValidatePatternErrorMessage,
  	}
  	options.apply(opts)
  
  	if str, ok := val.(string); ok {
  		match, _ := regexp.MatchString(pattern, str)
  		if !match {
  			msg := strings.Replace(options.message, "{field}", field, 1)
  			AddError(ch, field, msg)
  		}
  		return
  	}
  }
docs: // ValidatePattern validates the value of given field to match given pattern.