support combined futures bookticker ws event

v2/futures/websocket_service.go

@@ -572,6 +572,11 @@ type WsBookTickerEvent struct {
 	BestAskQty      string `json:"A"`
 }
 
+type WsCombinedBookTickerEvent struct {
+	Data   *WsBookTickerEvent `json:"data"`
+	Stream string             `json:"stream"`
+}
+
 // WsBookTickerHandler handle websocket that pushes updates to the best bid or ask price or quantity in real-time for a specified symbol.
 type WsBookTickerHandler func(event *WsBookTickerEvent)
 
@@ -591,6 +596,25 @@ func WsBookTickerServe(symbol string, handler WsBookTickerHandler, errHandler Er
 	return wsServe(cfg, wsHandler, errHandler)
 }
 
+func WsCombinedBookTickerServe(symbols []string, handler WsBookTickerHandler, errHandler ErrHandler) (doneC, stopC chan struct{}, err error) {
+	endpoint := getCombinedEndpoint()
+	for _, s := range symbols {
+		endpoint += fmt.Sprintf("%s@bookTicker", strings.ToLower(s)) + "/"
+	}
+	endpoint = endpoint[:len(endpoint)-1]
+	cfg := newWsConfig(endpoint)
+	wsHandler := func(message []byte) {
+		event := new(WsCombinedBookTickerEvent)
+		err := json.Unmarshal(message, event)
+		if err != nil {
+			errHandler(err)
+			return
+		}
+		handler(event.Data)
+	}
+	return wsServe(cfg, wsHandler, errHandler)
+}
+
 // WsAllBookTickerServe serve websocket that pushes updates to the best bid or ask price or quantity in real-time for all symbols.
 func WsAllBookTickerServe(handler WsBookTickerHandler, errHandler ErrHandler) (doneC, stopC chan struct{}, err error) {
 	endpoint := fmt.Sprintf("%s/!bookTicker", getWsEndpoint())