Authenticate Google Cloud Function Call outside GCP Environment - authentication

Question

I am trying to call a google cloud function on the In Contact Studio to fulfill a logic in my IVR Call, but I am unable to do that as I have closed public access to my cloud function, and now I am not getting a way how to authenticate the call.
I tried using the command gcloud auth print-identity-token to get a ID_TOKEN But this ID_TOKEN will be refreshed every time and I can't use this again and again, so is there any way that I can generate a ID_TOKEN every time I try to call this function using a simple API Call??
OR
Is there any other way to solve my problem?
Ways I have Tried :-
I have gone through this Documentation:- https://cloud.google.com/functions/docs/securing/authenticating#end-users
and I was using the access style of End-User But it is a way in which the access token was getting generated via login using browser, I want to do everything via code, cause it will be used as a backend code for IVR(call facility for assistance in various tasks), in this method also we get a access token and not a ID_TOKEN, whereas to invoke a function we need a ID_TOKEN and not a access token.
Secondly I tried the gcloud auth print-identity-token command on the google cloud shell where i was logged in with my google account so it generated the JWT token and I used it as a bearer token and the function worked, but how can I generate the token outside GCP or get the on frequent intervals via code.
I want a program way(NodeJS) of doing this and not a UI way, cause I need to attach this with backend of my program, and all the ways I have gone through on the internet have the only way is through UI, and none of them have a program way for outside GCP environment, so i need help on this scenario.

Answer 1

As John said, you can use the Google Doc code example to perform an URL call: The library generate a secure HTTP client to generate request to your endpoint.
If you want to generate the token and use it by yourselve, you can use this piece of code
const {GoogleAuth} = require('google-auth-library');
const auth = new GoogleAuth()
auth.getIdTokenClient("").then(client => {
client.idTokenProvider.fetchIdToken("audience").then(token => {
console.log(token)
})
})