feat(ws): WebSocket 核心模块（Hub + Client + PubSub + Handler）

- pkg/ws/message.go: 统一消息协议（Message/Response/PushMessage）
- pkg/ws/hub.go: Hub 连接管理（注册/注销/按 userID 查找/在线计数）
- pkg/ws/client.go: 客户端连接封装（readPump/writePump/心跳 30s）
- pkg/ws/pubsub.go: Redis Pub/Sub 消息路由（按用户频道发布/订阅）
- app/ws/handler.go: WebSocket 升级处理（JWT 认证 + 消息分发）
- app/ws/router.go: GET /ws 路由注册
- app/ws/provider.go: Wire Provider Set
- 更新 provider/router 集成 WebSocket 模块

Made-with: Cursor

backend/go-service/pkg/ws/pubsub.go

@@ -0,0 +1,98 @@
+package ws
+
+import (
+	"context"
+	"fmt"
+	"sync"
+
+	"github.com/echochat/backend/pkg/logs"
+	"github.com/redis/go-redis/v9"
+	"go.uber.org/zap"
+)
+
+const channelPrefix = "echo:ws:channel:"
+
+// PubSub 封装 Redis Pub/Sub，提供按用户频道的消息发布和订阅
+type PubSub struct {
+	rdb         *redis.Client
+	hub         *Hub
+	subs        map[int64]context.CancelFunc // userID -> 订阅取消函数
+	mu          sync.Mutex
+}
+
+// NewPubSub 创建 PubSub 实例
+func NewPubSub(rdb *redis.Client, hub *Hub) *PubSub {
+	return &PubSub{
+		rdb:  rdb,
+		hub:  hub,
+		subs: make(map[int64]context.CancelFunc),
+	}
+}
+
+// channelName 生成用户专属的 Redis 频道名
+func channelName(userID int64) string {
+	return fmt.Sprintf("%s%d", channelPrefix, userID)
+}
+
+// Publish 向指定用户的频道发布消息
+func (ps *PubSub) Publish(ctx context.Context, userID int64, data []byte) error {
+	channel := channelName(userID)
+	return ps.rdb.Publish(ctx, channel, data).Err()
+}
+
+// Subscribe 订阅指定用户的频道
+// 收到消息后自动转发给本地 Hub 中对应的 Client
+func (ps *PubSub) Subscribe(userID int64) {
+	ps.mu.Lock()
+	if cancel, ok := ps.subs[userID]; ok {
+		cancel()
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	ps.subs[userID] = cancel
+	ps.mu.Unlock()
+
+	channel := channelName(userID)
+	sub := ps.rdb.Subscribe(ctx, channel)
+
+	go func() {
+		defer sub.Close()
+		ch := sub.Channel()
+
+		logs.Info(nil, "ws.pubsub.Subscribe", "开始订阅用户频道",
+			zap.Int64("user_id", userID), zap.String("channel", channel))
+
+		for {
+			select {
+			case <-ctx.Done():
+				logs.Info(nil, "ws.pubsub.Subscribe", "取消订阅用户频道",
+					zap.Int64("user_id", userID))
+				return
+			case msg, ok := <-ch:
+				if !ok {
+					return
+				}
+				ps.hub.SendToUser(userID, []byte(msg.Payload))
+			}
+		}
+	}()
+}
+
+// Unsubscribe 取消订阅指定用户的频道
+func (ps *PubSub) Unsubscribe(userID int64) {
+	ps.mu.Lock()
+	defer ps.mu.Unlock()
+
+	if cancel, ok := ps.subs[userID]; ok {
+		cancel()
+		delete(ps.subs, userID)
+	}
+}
+
+// PublishToUser 便捷方法：序列化推送消息并发布到用户频道
+func (ps *PubSub) PublishToUser(ctx context.Context, userID int64, msg *PushMessage) error {
+	data, err := MarshalPush(msg)
+	if err != nil {
+		return fmt.Errorf("序列化推送消息失败: %w", err)
+	}
+	return ps.Publish(ctx, userID, data)
+}