log

type Logger interface {
	Debugf(format string, args ...interface{})

	Infof(format string, args ...interface{})

	Warnf(format string, args ...interface{})

	Fatalf(format string, args ...interface{})

	Errorf(format string, args ...interface{})

	Donef(format string, args ...interface{})

	StartWait(message string)
	StopWait()

	// Sync flushes cached log to disk, some log library needs this step
	Sync()
}