session.go
func (a *App) getSession(r *http.Request, w http.ResponseWriter) *Session {
	if a.root != nil {
		return a.root.getSession(r, w)
	}
	session, _ := a.SessionStore.Get(r, a.SessionName)
	return &Session{
		Session: session,
		req:     r,
		res:     w,
	}
}
func (a *App) getSession(r *http.Request, w http.ResponseWriter) *Session {
	if a.root != nil {
		return a.root.getSession(r, w)
	}
	session, _ := a.SessionStore.Get(r, a.SessionName)
	return &Session{
		Session: session,
		req:     r,
		res:     w,
	}
}
// Get a session using a request and response.