为什么此大猩猩会话代码不起作用？

I'm a golang noob, so I'm making my first toy app by setting up a seed project for a gorilla based web app. It's going well but the session code doesn't work as I expect it to, here is the full code, and here is just the relevant snippet:

func getMyCounter(w http.ResponseWriter, r *http.Request){
    session, _ := sessionStore.Get(r, counterSession)
    if session.IsNew {
        session.Values[myCounter] = 0
    }
    val := session.Values[myCounter].(int)
    log.Printf("getMyCounter %d", val)
    m := make(map[string]int)
    m["counter"] = val
    js, _ := json.Marshal(m)
    w.Header().Set("Content-Type", "application/json")
    w.Write(js)
}

func incrementMyCounter(w http.ResponseWriter, r *http.Request){
    log.Println("incrementMyCounter")
    session, _ := sessionStore.Get(r, counterSession)
    if session.IsNew {
        session.Values[myCounter] = 0
    }
    val := session.Values[myCounter].(int)
    session.Values[myCounter] = val + 1
    getMyCounter(w, r)
}

my calls to getMyCounter and incrementMyCounter always return 0

thanks to JimB for pointing out the painfully obvious, I needed to add a call to session.Save(r, w) after creating/editing the session.