You can now export your products to the Google Shopping feed format. This option is available in the 'Export Product Data' section of the app, just choose the Google Shopping Feed format when you are configuring your export.
The generated file will contain tab-separated data (a TSV file) in the format that Google needs to display your products in Google Shopping. The values used in the feed are extracted from your product data and you can customize them with metafields.
You can also take advantage of recurring exports to create a Google Shopping feed that's continously updated and sent to Google Merchant Center.
Learn more about exporting your Shopify products to Google Shopping.