         return nsp + "#" + (engine?.sid ?? "")
     }
 
-    private let emitQueue = DispatchQueue(label: "com.socketio.emitQueue", attributes: DispatchQueueAttributes.serial)
+    private let emitQueue = DispatchQueue(label: "com.socketio.emitQueue", attributes: .serial)
     private let logType = "SocketIOClient"
-    private let parseQueue = DispatchQueue(label: "com.socketio.parseQueue", attributes: DispatchQueueAttributes.serial)
+    private let parseQueue = DispatchQueue(label: "com.socketio.parseQueue", attributes: .serial)
 
     private var anyHandler: ((SocketAnyEvent) -> Void)?
     private var currentReconnectAttempt = 0


        handlers.append(handler)

        return handler.id as UUID
    }

    /// Adds a handler that will be called on every event.

        let handler = SocketEventHandler(event: event, id: UUID(), callback: callback)
        handlers.append(handler)

        return handler.id
    }

    /// Adds a single-use handler for an event.
