Refactor code and fix linter warnings (#3627)

* refactor: use any instead of empty interface

* refactor: code cleanup

sub/subJsonService.go

@@ -4,6 +4,7 @@ import (
 	_ "embed"
 	"encoding/json"
 	"fmt"
+	"maps"
 	"strings"
 
 	"github.com/mhsanaei/3x-ui/v2/database/model"
@@ -197,9 +198,8 @@ func (s *SubJsonService) getConfig(inbound *model.Inbound, client model.Client,
 
 		newOutbounds = append(newOutbounds, s.defaultOutbounds...)
 		newConfigJson := make(map[string]any)
-		for key, value := range s.configJson {
-			newConfigJson[key] = value
-		}
+		maps.Copy(newConfigJson, s.configJson)
+
 		newConfigJson["outbounds"] = newOutbounds
 		newConfigJson["remarks"] = s.SubService.genRemark(inbound, client.Email, extPrxy["remark"].(string))