Save scores into Firestore, using Go Functions
More information on https://medium.com/@feloy/firebase-saving-scores-into-firestore-with-go-functions-b128fd8c425
To publish the function:
gcloud beta functions deploy newScore \
--entry-point OnNewScore \
--memory 256MB \
--region us-central1 \
--runtime go111 \
--trigger-event providers/cloud.firestore/eventTypes/document.create \
--trigger-resource "projects/<your-project-id>/databases/(default)/documents/Score/{id}"