glg.go
func SuccessFunc(f func() string) error {
	if isModeEnable(OK) {
		return glg.out(OK, "%s", f())
	}
	return nil
}
func SuccessFunc(f func() string) error {
	if isModeEnable(OK) {
		return glg.out(OK, "%s", f())
	}
	return nil
}
// SuccessFunc outputs Success level log returned from the function