// app.js
angular
        .module('appName', ['ngRoute'])
        .constant('config', {
            GOOGLE_KEY: ':)'
        })
        .config(routes);

// service.js
angular
        .module('appName')
        .factory('serviceName', serviceName);

    serviceName.$inject = ['$http'];

    function serviceName($http, config) {

        console.log(config);

        ..