firestore node.js sdk stops responding on write - node.js

Question

I am building a CLI app where I want to use firebase as the backend. I am using the firebase node.js sdk for this and I am running into a problem where after successful login, the firestore add / set functions stop responding and do not trigger either the "then" method or the "error" method.
const firebase = require('firebase');
// Your web app's Firebase configuration
var firebaseConfig = {
apiKey: "<REDACTED>",
authDomain: "<REDACTED>",
databaseURL: "<REDACTED>",
projectId: "<REDACTED>",
storageBucket: "<REDACTED>",
messagingSenderId: "<REDACTED>",
appId: "<REDACTED>"
};
// Initialize Firebase
var app = firebase.initializeApp(firebaseConfig);
function main() {
firebase.auth().signInWithEmailAndPassword('username', 'somepassword').then((cred) => {
console.log('Successful sign in');
firebase.firestore().collection('UserData').doc(cred.user['uid']).collection('ShellCommands').add({'Hello': 'World'}).then(function() {
console.log("Document successfully written!");
terminate();
}).catch(function(error) {
console.log(error);
});
}).catch(function(error) {
console.log(error);
});
}
main();
Now when I run this, I do see the successful sign in console log but after that the app stops and doesn't respond. It seems like its waiting for user input since the keyboard is active.
My firestore rules are open (for testing).
rules_version = '2';
service cloud.firestore {
match /databases/{database}/documents {
match /{document=**} {
allow read, write;
}
}
}
Am wondering if I messed up chaining the promise or is there something fundamentally wrong with doing it this way. Note, this will not be a server but a CLI app.
[EDITED]: The CLI app gets passed a string which it writes to firestore and exits. So everytime, the CLI is run, it would login and write the string. However, the CLI would be per user, so the user is only allowed to write to their collection. something like UserData/{UserID}/Data.