log/log.go
func Warnf(format string, args ...interface{}) {
	logger.Output(2, LevelWarn, fmt.Sprintf(format, args...))
}
func Warnf(format string, args ...interface{}) {
	logger.Output(2, LevelWarn, fmt.Sprintf(format, args...))
}
// Warnf records the log with warn level