Gaining access to an app's config file from an addon can be challenging. If possible, you should always get it through the container like so:

export default Ember.Component.extend({
  someFunction() {
    const config = Ember.getOwner(this).resolveRegistration('config:environment');
    . . . .
  }
});

If you do not have access to the container though, you can always use ember-get-config.

ember install ember-get-config

Simply:

import config from 'ember-get-config';

Which allows you to do handy things like:

const { environment, modulePrefix } = config;

Boom!

See the Contributing guide for details.