best way to add user_id

[MicahDavid]

Look for best way to add user_id to gtag config?

It doesn't seem possible to add the user_id inside nuxt.config.js like below, since I need the $auth object?

    'google-gtag': {
        id: 'G-XXXXXXX',
        config:{
            user_id: xxx
        },
    },

It does look like I can call the gtag config method elsewhere in my code. Will this accomplish the goal of tracking all page views with the user_id including the initial page view with the user_id?

      this.$gtag("config", "UA-XXXXXXX", {
        user_id: (this.$auth.loggedIn) ? this.$auth.$state.user.id : null,
      });

I am adding the above config call when the app header component is mounted. Please suggest if there is a better place to put this.

-- EDIT--
It looked like in the documentation, that instead of calling config twice, I should be calling the set method like this:

 this.$gtag('set','user_id',xxx)

This, however doesn't seem to work in analytics data.