refactor: update logging related logic

common/init.go

@@ -12,7 +12,7 @@ var (
 	Port         = flag.Int("port", 3000, "the listening port")
 	PrintVersion = flag.Bool("version", false, "print version and exit")
 	PrintHelp    = flag.Bool("help", false, "print help and exit")
-	LogDir       = flag.String("log-dir", "", "specify the log directory")
+	LogDir       = flag.String("log-dir", "./logs", "specify the log directory")
 )
 
 func printHelp() {