app.json

{
  "expo": {
    /...*/
    "description": "Basic Firebase Login",
    "githubUrl": "https://github.com/popeating/FirebaseLogin",
    /*ADD DATA IN EXTRA SECTION*/
    "extra": {
      "IOS_KEY": "",
      "ANDROID_KEY": "",
      "API_KEY": "",
      "AUTH_DOMAIN": "",
      "DATABASE_URL": "",
      "PROJECT_ID": "",
      "STORAGE_BUCKET": "",
      "MESSAGE_SENDER_ID": "",
      "APP_ID": ""
    }
  }
}