is GO source code uploaded to google app engine?

I'm wondering if the source code is uploaded or only the binary / compiled version ? Do GAE engineers have access to my precious source code ?

What is Go App Engine?

Google App Engine is a service and a platform where you can develop and host web applications. You can learn more about Google App Engine at the official Google App Engine site. With App Engine integration, you can run and debug Google App Engine applications. A new project already includes app.

The source code appears to be uploaded as well, according to "Downloading source code" in Uploading, Downloading, and Managing a Go App. You could prove it by trying to download the source code yourself.

Yes it uploads the source code and you can also download the source code of a specific version you previously deployed. You can also PERMANENTLY disable such a feature in the admin page. Don't worry to upload it, besides having strict SLA no one really cares about your code.