Q:

Can I deploy different programming languages as Microservices (modules) on standard GAE? 

I currently use the standard GAE (PHP-based application) for a while.  Regarding GAE provides the Microservices such as setting the module name and version in app.yaml where I can run different services in the same application.  
However, I wanna run PHP, say in module A, run Golang in module B and run Python in module C. Is it possible to deploy different programming languages in the same application as Microservices?    

A:

Yes, it is possible to have different modules, now called services[1] in GAE, in the same application configured with different runtimes and different performance settings, deployed as microservices. 
You can deploy code to each service independently and have each service written in a different programming language, such as Python, Java, Go and PHP[1].  It is also possible to have versions within services[2], as each service can have more than one version deployed at the same time. To execute code on the different services you will have to do it through an HTTP invocation or an RESTful API call.