func (c *Connection) newMuxClient(ctx context.Context) (*muxClient, error) {
	client := newMuxClient(ctx, atomic.AddUint64(&c.NextID, 1), c)
	if dl, ok := ctx.Deadline(); ok {
		client.deadline = getDeadline(time.Until(dl))
		if client.deadline == 0 {
			client.cancelFn(context.DeadlineExceeded)
			return nil, context.DeadlineExceeded
		}
	}
	for {
		// Handle the extremely unlikely scenario that we wrapped.