var Botkit = require('botkit'),
    datastoreStorage = require('botkit-storage-datastore')({projectId: '...'}),
    controller = Botkit.slackbot({
        storage: datastoreStorage
    });

// then you can use the Botkit storage api, make sure you have an id property
var beans = {id: 'cool', beans: ['pinto', 'garbanzo']};
controller.storage.teams.save(beans);
beans = controller.storage.teams.get('cool');