func (c *Connection) Subroute(s string) *Subroute {
	if c == nil {
		return nil
	}
	return &Subroute{
		Connection: c,
		route:      s,
		subID:      makeSubHandlerID(0, s),
		trace:      c.trace.subroute(s),
	}
}

// Subroute adds a subroute to the subroute.
// The subroutes are combined with '/'.
func (c *Subroute) Subroute(s string) *Subroute {