No Service Base Class

controllers.application\.js

import Controller from '@ember/controller';
import { inject as service } from '@ember/service';

export default class ApplicationController extends Controller {
  @service foo;
}

services.bar\.js

export default class BarService {
  hello = 'Hello World';

  constructor(injections) {
    Object.assign(this, injections);
  }

  static create(injections) {
    return new this(injections);
  }
}

services.foo\.js

import { inject as service } from '@ember/service';

export default class FooService {
  @service bar;

  constructor(injections) {
    Object.assign(this, injections);
  }

  static create(injections) {
    return new this(injections);
  }
}

templates.application\.hbs

{{this.foo.bar.hello}}

twiddle\.json

{
  "version": "0.16.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.14.3",
    "ember-template-compiler": "3.14.3",
    "ember-testing": "3.14.3"
  },
  "addons": {
    "ember-data": "3.14.1"
  }
}