var responseBuilder: Response.Builder? = null
    var sendRequestException: IOException? = null
    val hasRequestBody = HttpMethod.permitsRequestBody(request.method) && requestBody != null
    val isUpgradeRequest =
      !hasRequestBody &&
        "upgrade".equals(request.header("Connection"), ignoreCase = true)
    try {
      exchange.writeRequestHeaders(request)

      if (hasRequestBody) {