if ("100-continue".equals(request.header("Expect"), ignoreCase = true)) {
          exchange.flushRequest()
          responseBuilder = exchange.readResponseHeaders(expectContinue = true)
          exchange.responseHeadersStart()
          invokeStartEvent = false
        }
        if (responseBuilder == null) {
          if (requestBody.isDuplex()) {

  }

  fun responseHeadersStart() {
    call.eventListener.responseHeadersStart(call)
  }

  @Throws(IOException::class)
  fun readResponseHeaders(expectContinue: Boolean): Response.Builder? {
    try {
      val result = codec.readResponseHeaders(expectContinue)
      result?.initExchange(this)
      return result
    } catch (e: IOException) {
      call.eventListener.responseFailed(call, e)
      trackFailure(e)