func example() {
var ctx context.Context
// [START intro]
if !capability.Enabled(ctx, "datastore_v3", "write") {
// Datastore is in read-only mode.
}
// [END intro]
}
// [START datastore_lookup]
func handler(w http.ResponseWriter, r *http.Request) {
ctx := appengine.NewContext(r)
if !capability.Enabled(ctx, "datastore_v3", "*") {
http.Error(w, "This service is currently unavailable.", 503)
return
}
// do Datastore lookup ...
}