golang会话变量不起作用

Question

I tried the following code. The first time I opened the page, the username is nil and the next time, the value turned to be a real name.

func sayHello(w http.ResponseWriter, r *http.Request) {
    sess, _ := globalSessions.SessionStart(w, r)
    defer sess.SessionRelease(w)
    username := sess.Get(r.FormValue("name"))
    fmt.Println(username)
    sess.Set(r.FormValue("name"), r.FormValue("name"))
}

However, when I am going to implement some complex function, the session does not work.

func loginHandler(w http.ResponseWriter, r *http.Request) {
    var (
            query      url.Values
            err        error
            userInfo   daomanage.User
            statusInfo StatusInfo
        )   

    cookie, err := r.Cookie("gosessionid")
    sess, _ := globalSessions.SessionStart(w, r)
    defer sess.SessionRelease(w)
    sessionCache := sess.Get(cookie.Value)
    log.Println("newcache", sessionCache, cookie.Value)
    sess.Set(cookie.Value, cookie.Value)

    // symbol xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

    if sessionCache != nil {
        statusInfo.Status = 200 
        statusInfo.Info = userInfo.Username
        data, _ := json.Marshal(statusInfo)
        fmt.Fprintf(w, string(data))
        return
    }   

    query, err = url.ParseQuery(r.URL.RawQuery)
    if err != nil {
        log.Println("Parse Error", err)
        return
    }   

    // Get user info
    if s, ok := query["username"]; ok {
        userInfo, err = daomanage.GetUserInfo("username", s[0])
        if err == nil {
            if p, ok := query["password"]; ok {
                if p[0] == userInfo.Password {
                    sess.Set(s[0], s[0])
                    log.Println(sess.Get(s[0]))

                    tNow := time.Now()
                    cookie := http.Cookie{Name: "gosessionid", Value: s[0], Expires: tNow.AddDate(1, 0, 0)}
                    http.SetCookie(w, &cookie)

                    statusInfo.Status = 200
                    statusInfo.Info = userInfo.Username
                    data, _ := json.Marshal(statusInfo)
                    fmt.Fprintf(w, string(data))
                    return
                }
            }
        }
    }
    statusInfo.Status = 400
    statusInfo.Info = InfoLoginFailed
    data, _ := json.Marshal(statusInfo)
    fmt.Fprintf(w, string(data))
    return
}

I send the query to the function again and again, but the function sess.Get(cookie.Value) returns nothing. I even tried to set the session right after the get function(because in the demo, it works), it still does not work.

When I deleted the code below the symbol, it works again!

Are there any problems? Please help!