修正groupby字段读取逻辑

cmd/saastool/exp_get.go

@@ -97,7 +97,7 @@ func RunExpGet(args ...string) error {
 	groupBySlice := []string{}
 	if *groupBy != "" {
 		validGroupBy := map[string]bool{"advertiser_id": true, "user_weight_factor": true}
-		groupBySlice := strings.Split(*groupBy, ",")
+		groupBySlice = strings.Split(*groupBy, ",")
 		for _, group := range groupBySlice {
 			if !validGroupBy[group] {
 				fmt.Fprintln(os.Stderr, "group by error", "group", group)