How to use GraphQL extension service .use() in strapi-server.js

Following the guide here::

I have managed to successfully extend my GraphQL schema inside the register function at /src/index.js.

Currently the schema has grown a little out of hand so I’ve decided I want to move things around to clean it up. I’d like to register the extension to grapgql in /src/extensions/graphql but I’ve run into a small problem. The graphql plugin object(shown below) passed to the strapi-server.js file is a function(which does return an object containing use but I’ve tried calling it and then calling use() and it doesn’t seem to work.) and calling strapi.plugin(‘graphql’) returns undefined. I suppose at this point in the startup of the app(before register is called) the plugin/strapi hasn’t been fully bootstrapped and that’s why it’s unavailable.

Question: How can I register an extension to the graphql schema from /src/extensions/graphql/strapi-server?

GraphQL Plugin **in strapi-server.js** function export
  config: {
  bootstrap: [AsyncFunction (anonymous)],
  services: {
    builders: [Function (anonymous)],
    'content-api': [Function (anonymous)],
    constants: [Function (anonymous)],
    extension: [Function: createExtension],
    format: [Function (anonymous)],
    internals: [Function (anonymous)],
    'type-registry': [Function (anonymous)],
    utils: [Function (anonymous)]
  destroy: [Function: destroy],
  register: [Function: register],
  routes: [],
  controllers: {},
  policies: {},
  middlewares: {},
  contentTypes: {}