you already could connect to cloudsql instances. however you needed a proxy, but not because of AppEngine, you need it because of security. either you whitelis

you already could connect to cloudsql instances. however you needed a proxy, but not because of AppEngine, you need it because of security. either you whitelisted your ips or you used the proxy (which go appengine could already use). so with go you just needed to use https://github.com/GoogleCloudPlatform/cloudsql-proxy https://github.com/GoogleCloudPlatform/cloudsql-proxy which means you just need to change the query string. however a new feature is emerging where you can have a private ip that is connected to your internal services, however it is still a beta feature. Source: myself, but not a googler, just a regular user