log/log.go
func (t *Target) Debugf(format string, v ...interface{}) {
	t.mut.RLock()
	defer t.mut.RUnlock()
	if t.logger != nil {
		t.logger.Debugf(format, v...)
	}
}
func (t *Target) Debugf(format string, v ...interface{}) {
	t.mut.RLock()
	defer t.mut.RUnlock()
	if t.logger != nil {
		t.logger.Debugf(format, v...)
	}
}
// Debugf writes the formatted string to the Target
// logger.