Go App Boilerplate on App Engine Standard go 1.11 runtime

Get started with Go 1.11 Standard by reading documentation here. You'll need to create an App Engine project of course.
Define your app.yaml runtime settings.
Build your Create React App with $ npm run build to create the build directory.
Define your server and routing in your main.go file, and since we're serving up a Create React App front-end We're pointing the server to the ./build directory for static files.
For deploying go 1.11, we're using the go.mod method instead of the former GOPATH method. See documentation on that update here.
Use the following commands to create a go.mod before deployment:

$ export GO111MODULE=on  # required to use this module method
$ go mod init
$ go mod tidy

Setting Up Firebase Firestore

Make sure you enable Google Cloud Firestore API in the API's & Services section of your Google Cloud Platform project.
Make sure you setup and enable your Cloud Firestore database in your Firebase console in the Database tab.
For more info on how to set up your firebase service account firebase.json file, go here. You generate the json keys here: https://console.firebase.google.com/u/1/project/<your_firebase_project_id>/settings/serviceaccounts/adminsdk
For use of other project flags and services with gcloud deployments, define those in your deploy.sh file.
Finally, deploy your app with $ npm run deploy.