Hello, this is a weird error to have as appengine.Main() is a call used by many go applications, so it is definitely expected to work just fine for you. The fact that you're the only person to have reported this issue in the year that it has affected you makes me suspect that there might be an issue with either your application's configuration or your environment.
To make sure the problem isn't with your environment you might want to upload your application to the
Cloud Shell and deploy it from there.
If you're also getting deployment errors on the Cloud Shell could you tell us more about your app's configuration and the commands you're using to test and deploy it?
Also please note that this type of question is probably more suited for
Stack Overflow where you would also be asked for more information.