I see that the POSTGRES database option for gce sql is still in BETA, just looking for confermation that the issue mentioned below is an issue with the API and not something stupid I've overlooked.
gcloud sql instances create example-db --activation-policy=ALWAYS --tier="db-n1-standard-1" --pricing-plan="PER_USE" --region="asia-east1" --gce-zone="asia-east1-a" --database-version=POSTGRES_9_6
HTTPError 400: Invalid value for: POSTGRES_9_6 is not a valid value
Documentation says that this is a valid option: - https://cloud.google.com/sdk/gcloud/reference/sql/instances/create