initialize-firebase-without-using-google-services-json

[ayyysh04]

I am trying to initialize and connect my app to firebase realtime database without using the google-services plugin
I am referring to this - https://firebase.googleblog.com/2017/03/take-control-of-your-firebase-init-on.html
but this isn't helping me.

My code :
FirebaseOptions options = new FirebaseOptions(
apiKey: "",
appId: "value",
projectId: "value",
messagingSenderId: 'value',
databaseURL: "value",
storageBucket: "value",
androidClientId:
"value");
final FirebaseApp firebase =
await Firebase.initializeApp(options: options);

but this is given error that:
Exception has occurred.
_CastError (Null check operator used on a null value)

Plz help