add SetLogLevelByName

log.go

@@ -94,9 +94,9 @@ func (log *Logger) SetLogLevel(newlv LogLevel) (oldlv LogLevel) {
 // SetLogLevelByName set new log level by level name
 func (log *Logger) SetLogLevelByName(newlv string) (oldlv string) {
 	if newlevel, ok := mapStrToLevel[newlv]; ok {
-		oldlv = log.loglevel
+		oldlevel := log.loglevel
 		log.loglevel = newlevel
-		return mapLevelToStr[oldlv]
+		return mapLevelToStr[oldlevel]
 	}
 	return ErrLogLevel
 }