feat: 实现网关服务的长连接功能

backend/gateway/internal/ws/message.go

@@ -0,0 +1,18 @@
+package ws
+
+type MessageType string
+
+const (
+	MessageTypePing    MessageType = "ping"
+	MessageTypePong    MessageType = "pong"
+	MessageTypeText    MessageType = "text"
+	MessageTypeError   MessageType = "error"
+	MessageTypeCommand MessageType = "command"
+)
+
+type Message struct {
+	Type    MessageType `json:"type"`
+	Content string      `json:"content,omitempty"`
+	Data    interface{} `json:"data,omitempty"`
+	Error   string      `json:"error,omitempty"`
+}