reflectutil

var TitleUnderscore ToMapKey = func(raw string) string {
	newstr := make([]rune, 0, len(raw))
	for i, chr := range raw {
		if isUpper := 'A' <= chr && chr <= 'Z'; isUpper {
			if i > 0 {
				newstr = append(newstr, '_')
			}
			chr -= 'A' - 'a'
		}
		newstr = append(newstr, chr)
	}
	return string(newstr)
}