utils/log: support max days of keeping log files

src/frp/models/client/config.go

@@ -28,6 +28,7 @@ var (
 	LogFile           string = "console"
 	LogWay            string = "console"
 	LogLevel          string = "info"
+	LogMaxDays        int64  = 3
 	HeartBeatInterval int64  = 20
 	HeartBeatTimeout  int64  = 90
 )
@@ -69,6 +70,11 @@ func LoadConf(confFile string) (err error) {
 		LogLevel = tmpStr
 	}
 
+	tmpStr, ok = conf.Get("common", "log_max_days")
+	if ok {
+		LogMaxDays, _ = strconv.ParseInt(tmpStr, 10, 64)
+	}
+
 	var authToken string
 	tmpStr, ok = conf.Get("common", "auth_token")
 	if ok {