X-appengine-inbound-appid Header Is Not Added In Gae Flexible Environment

According to https://cloud.google.com/appengine/docs/flexible/go/migrating#url_fetch ,in flexible environment we can use http lib instead of urlFetch which is supposed to add GAE r

Solution 1:

I did some research and created a case for GAE tech support's help.

Yes, this is indeed working as intended, this header is provided by the UrlFetch service, which isn't used on this case so there isn't a component to append this header.

Above is what I heard from GAE support. So... I believe "X-Appengine-Inbound-Appid" header for flex env is not available.