*/
  @Throws(IOException::class)
  fun shutdown(statusCode: ErrorCode) {
    writer.withLock {
      val lastGoodStreamId: Int
      withLock {
        if (isShutdown) {
          return
        }
        isShutdown = true
        lastGoodStreamId = this.lastGoodStreamId
      }
      // TODO: propagate exception message into debugData.