If your react native expo application needs to access google services (such as google maps) you will need to create a google api key. The problem is this api key must remain hidden from the public or you risk receiving a large unannounced bill from Google.

You also do not want the api key embedded in the client application as this can be extracted by a determined hacker.

Fortunately this is pretty easy.

Open a terminal and enter

• eas init

This is will generate an app.json file or if you already have one, it will add extra.eas.projectId to app.json

• Rename your app.json file to app.config.js.

Now edit app.config.js, it should something like this.

First notice line 1. Since this is a js file we must export the json. Add export default {...}

Now note line 40: "apiKey": process.env.GOOGLE_SERVICES_API

GOOGLE_SERVICES_API is the secret variable we must now create on expo.dev

Login to your expo.dev account, click secrets, and add the new variable GOOGLE_SERVICES_API and set the value to your google api key.

Go back to your terminal and type

• eas secret:list

you should see something like:

Secrets for this account and project:
ID          30af395a-70bb-4b33-afe7-xxxxxxxxxxx
Name        GOOGLE_SERVICES_API
Scope       project
Type        STRING
Updated at  Oct 03 11:29:30

That's it! Now you can checkin your files to a public repository with no worries of a hacker exploiting your google api key.