Getting FCM Access token

[Ori Idan]

I am looking for a simple method to get the Access token.

The only method that I could find working is using the gcloud command but this is slow.

What is the best way to get the Access token?

I tried using this url:
https://www.googleapis.com/firebase/v1/projects/my-project-id/accounts/serviceAccount:generateAccessToken

But could not find what to put in my-project-id, I tried using the project id that I used to send FCM messages and it gave me 404 error. I have no idea how to find the right project-id.

This method also requires an Access token and I have no idea where to get this access token.