masterVersion property

The Kubernetes version to change the master to.

Users may specify either explicit versions offered by Kubernetes Engine or version aliases, which have the following behavior: - "latest": picks the highest valid Kubernetes version - "1.X": picks the highest valid patch+gke.N patch in the 1.X version - "1.X.Y": picks the highest valid gke.N patch in the 1.X.Y version - "1.X.Y-gke.N": picks an explicit Kubernetes version - "-": picks the default Kubernetes version

Required.