val request = Request(server.url("/a"))
    val call = client.newCall(request)
    call.enqueue(
      object : Callback {
        override fun onFailure(
          call: Call,
          e: IOException,
        ) {
          failureRef.set(true)
          latch.countDown()
        }

        override fun onResponse(
          call: Call,
          response: Response,
        ) {