//     RoundTripper returns.
	ctx, cancel := context.WithCancelCause(req.Context())

	// Convert Request.Cancel into context cancelation.
	if origReq.Cancel != nil {
		go awaitLegacyCancel(ctx, cancel, origReq)
	}

	// Convert Transport.CancelRequest into context cancelation.
	//
	// This is lamentably expensive. CancelRequest has been deprecated for a long time