Fix negative wallet balance (#53)

修复钱包余额小于扣款金额时，余额会变成负数的问题

wallet/wallet.go

@@ -73,15 +73,19 @@ func GetGroupWalletOf(sortable bool, uids ...int64) (wallets []Wallet, err error
 }
 
 // InsertWalletOf 更新钱包(money > 0 增加,money < 0 减少)
-func InsertWalletOf(uid int64, money int) error {
+func (sql *Storage) InsertWalletOf(uid int64, money int) error {
+	sql.Lock()
+	defer sql.Unlock()
 	lastMoney := sdb.getWalletOf(uid)
-	return sdb.updateWalletOf(uid, lastMoney.Money+money)
+	newMoney := lastMoney.Money + money
+	if newMoney < 0 {
+		newMoney = 0
+	}
+	return sdb.updateWalletOf(uid, newMoney)
 }
 
 // 获取钱包数据
 func (sql *Storage) getWalletOf(uid int64) (wallet Wallet) {
-	sql.RLock()
-	defer sql.RUnlock()
 	uidstr := strconv.FormatInt(uid, 10)
 	_ = sql.db.Find("storage", &wallet, "where uid is "+uidstr)
 	return
@@ -110,8 +114,6 @@ func (sql *Storage) getGroupWalletOf(sortable bool, uids ...int64) (wallets []Wa
 
 // 更新钱包
 func (sql *Storage) updateWalletOf(uid int64, money int) (err error) {
-	sql.Lock()
-	defer sql.Unlock()
 	return sql.db.Insert("storage", &Wallet{
 		UID:   uid,
 		Money: money,