val writer = Http2Writer(builder.sink, client)

  // Visible for testing
  val readerRunnable = ReaderRunnable(Http2Reader(builder.source, client))

  // Guarded by this.
  private val currentPushRequests = mutableSetOf<Int>()

  init {
    if (builder.pingIntervalMillis != 0) {
      val pingIntervalNanos = TimeUnit.MILLISECONDS.toNanos(builder.pingIntervalMillis.toLong())