The Functions as a Service space is rapidly growing, and there are a number of tools and frameworks to aid in developing in this new space. Perhaps the most popular of these is the Serverless Framework. The Serverless Framework allows developers to build and deploy functions in a cloud-agnostic manner. Support for Google Cloud is currently limited to HTTP triggers and Pub/Sub triggers (called events).
For organizations that are seriously considering a move to serverless architectures, it may be worth considering some of the open source FaaS solutions, many of which can be made to run on top of Kubernetes Engine. These platforms include OpenFaaS and Fission.