resc := make(chan res)
	go func() {
		fd, err := dialPlan9Blocking(ctx, net, laddr, raddr)
		select {
		case resc <- res{fd, err}:
		case <-ctx.Done():
			if fd != nil {
				fd.Close()
			}
		}
	}()
	select {
	case res := <-resc:
		return res.fd, res.err
	case <-ctx.Done():
		return nil, mapErr(ctx.Err())
	}
}