优化代码

internal/db/models/metric_stat_model_ext.go

@@ -6,7 +6,7 @@ import "encoding/json"
 func (this *MetricStat) DecodeKeys() []string {
 	var result []string
 	if len(this.Keys) > 0 {
-		_ = json.Unmarshal([]byte(this.Keys), &result)
+		_ = json.Unmarshal(this.Keys, &result)
 	}
 	return result
 }