fix(api): market/combined_streams: Get Proxy form Environment (#879)

* fix(api): market/combined_streams: Get Proxy form Environment

issues:
❌ 批量订阅流失败: 组合流WebSocket连接失败: dial tcp xxxxxx:443: i/o timeout

Make environment variables effective for
dialer.Dial("wss://fstream.binance.com/stream", nil):

export HTTPS_PROXY=http://ip:port
export HTTP_PROXY=http://ip:port

Signed-off-by: MarsDoge <mars@dogexorg.com>

* docs(WebSocket): add proxy usage guidance for combined streams (#475)

Signed-off-by: MarsDoge <mars@dogexorg.com>

---------

Signed-off-by: MarsDoge <mars@dogexorg.com>

market/combined_streams.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 	"sync"
 	"time"
+	"net/http"
 
 	"github.com/gorilla/websocket"
 )
@@ -32,6 +33,7 @@ func NewCombinedStreamsClient(batchSize int) *CombinedStreamsClient {
 func (c *CombinedStreamsClient) Connect() error {
 	dialer := websocket.Dialer{
 		HandshakeTimeout: 10 * time.Second,
+		Proxy           : http.ProxyFromEnvironment,
 	}
 
 	// 组合流使用不同的端点