```

feat(player): 优化金币兑换功能

- 在ServiceUpdate方法中返回更新后的数据而不是nil
- 新增DuihuanGold方法用于处理金币兑换逻辑
- 修改黄金列表控制器中的兑换计算逻辑，区分费用和获得金币的计算
- 在添加操作前验证用户金币余额是否充足
- 修正了兑换比例计算和余额检查逻辑
```

modules/player/service/gold_list.go

@@ -2,11 +2,13 @@ package service
 
 import (
 	"blazing/cool"
+	"blazing/modules/base/service"
 	"blazing/modules/player/model"
 	"context"
 	"fmt"
 
 	"github.com/gogf/gf/v2/frame/g"
+	"github.com/gogf/gf/v2/util/gconv"
 )
 
 type GoldListService struct {
@@ -17,8 +19,10 @@ func (s *GoldListService) ModifyBefore(ctx context.Context, method string, param
 	admin := cool.GetAdmin(ctx)
 	userId := admin.UserId
 
-	g.RequestFromCtx(ctx).SetParam("player_id", userId)
 	if method == "Add" {
+		if service.NewBaseSysUserService().GetGold(userId) < gconv.Int64(param["exchange_num"])*100 {
+			return fmt.Errorf("金额不足")
+		}
 
 		t, _ := s.dbm_fix(s.Model).Where("player_id", userId).Where("status", 0).Count()
 		if t > 0 {