code: func (f DateTimeFormatChecker) IsFormat(input interface{}) bool {
  	asString, ok := input.(string)
  	if !ok {
  		return false
  	}
  
  	formats := []string{
  		"15:04:05",
  		"15:04:05Z07:00",
  		"2006-01-02",
  		time.RFC3339,
  		time.RFC3339Nano,
  	}
  
  	for _, format := range formats {
  		if _, err := time.Parse(format, asString); err == nil {
  			return true
  		}
  	}
  
  	return false
  }
docs: // IsFormat checks if input is a correctly formatted  date/time per RFC3339 5.6