if (stream != null) return

    val hasRequestBody = request.body != null
    val requestHeaders = http2HeadersList(request)
    stream = http2Connection.newStream(requestHeaders, hasRequestBody)
    // We may have been asked to cancel while creating the new stream and sending the request
    // headers, but there was still no stream to close.
    if (canceled) {
      stream!!.closeLater(ErrorCode.CANCEL)
      throw IOException("Canceled")
    }