             let data = try encoder.encode(message)
             let str = String(data: data, encoding: .utf8)!
             Logger.debug(type: .signalingChannel, message: str)
-            webSocketChannel!.send(message: .text(str))
+            webSocketChannel.send(message: .text(str))
         } catch {
             Logger.debug(type: .signalingChannel,
                       message: "JSON encoding failed")

        }
    }
    
    var webSocketChannel: WebSocketChannel?

    private var connectionTimer: ConnectionTimer?
    private var onConnectHandler: ((Error?) -> Void)?

    /// クライアントの設定
    var configuration: Configuration { get }
    
    /// WebSocket チャネル
    var webSocketChannel: WebSocketChannel { get }
    
    /// 接続状態
    var state: SignalingChannelState { get }
