问为AppEngine提供程序更正OAuth2 Golang包

EN

"golang.org/x/net/context".Context does not implement "appengine".Context (missing Call method)

cannot use oauth2.NewClient(c) (type *http.Client) as type "golang.org/x/net/context".Context in argument to provider.Client:
*http.Client does not implement "golang.org/x/net/context".Context (missing Deadline method)

Post https://accounts.google.com/o/oauth2/token: not an App Engine context

func Public_YoutubeOauth(w http.ResponseWriter, r *http.Request) {
    c := appengine.NewContext(r)
    provider, csrf := getOAuth(r)
    gets, err := url.ParseQuery(r.URL.RawQuery)
    if RenderHtmlIfError(w,err) {
        return
    }
    if csrf != gets.Get(`state`) {
        RenderHtmlError(w,`incorrect CSRF state`)
        return
    }
    code := gets.Get(`code`)
    token, err := provider.Exchange(c, code) // error here
    if RenderHtmlIfError(w,err) {
        return
    }
    RenderHtml(w,`page`,map[string]interface{`token`:token})
}

&oauth2.Config{
        ClientID:     `aaa`,
        ClientSecret: `bbb`,
        RedirectURL:  url + `/foo/youtube_oauth`,
        Scopes: []string{
            `openid`,
            `email`,
            `profile`,
            `https://www.googleapis.com/auth/youtube`,
        },
        Endpoint: google.Endpoint,
    }