According to this
There is a Go library for Cloud SQL.
Google Cloud SQL on App Engine:
user@cloudsql(project-id:instance-name)/dbname
But according the GAE site, you can (maybe should?) use only java or python to connect to Cloud SQL: https://developers.google.com/cloud-sql/faq#languages
Can I use languages other than Java or Python?
Only Java and Python are supported for Google Cloud SQL.
I'm determining if GAE is a good fit for my Go application. Is Google discouraging the use of 3rd party libraries to connect to Cloud SQL?
Not being able to use Cloud SQL would be a deal breaker for me and will have me looking for another platform to host my Go application.
Using Google Cloud SQL with App Engine Go SDK
This document describes how to use Google Cloud SQL instances with the App Engine Go SDK.
Cloud SQL with Go-MySQL-Driver
We would like to add support for Cloud SQL to github.com/go-sql-driver/mysql.
There shouldn't be much to do. The appengine/cloudsql package 1 provides a Dial function that takes a CloudSQL instance name and returns a net.Conn; you just have to arrange for your mysql driver to call that (or have some way of taking a net.Conn).
You could follow what we did for ziutek's mymysql package 2.
Why do you think you have will have a problem?
I belive you can use 3rd packages, here is the document in Go specific App Engine API: https://developers.google.com/appengine/docs/go/cloud-sql/reference
Applications should use this package through database/sql: Select a pure Go MySQL driver that supports this package, and use sql.Open with protocol "cloudsql" and an address of the CloudSQL instance. The exact format of the second argument to sql.Open is driver-dependent; consult the driver's documentation for details.
import "database/sql"
import _ "<some mysql package>"
So I think "" can be https://github.com/go-sql-driver/mysql