Google Cloud SQL: driver: bad connection although different projects work - google-app-engine

Question

I am currently trying to deploy another app on GAE using a Google Cloud SQL instance. I already have 2 services running on there with the same setup also using a Cloudsql instance. However, when I am trying to connect to Cloudsql from my newest service, I am getting a "driver: bad connection" error and I can not figure out why. I am using the _ "github.com/go-sql-driver/mysql" driver as follows:
var (
DB_INSTANCE *sql.DB
)
...
configFile := GetConfig()
user := configFile.DatabaseReaderHost.DatabaseUser
password := configFile.DatabaseReaderHost.DatabasePassword
dbName := configFile.DatabaseReaderHost.DatabaseName
connectionName := "project-id:region:instance-name"
if appengine.IsDevAppServer() {
db, err := sql.Open("mysql", fmt.Sprintf("%s:%s#tcp(%s:%s)/%s?parseTime=true",
user,
password,
configFile.DatabaseReaderHost.DatabaseHost,
configFile.DatabaseReaderHost.DatabasePort,
dbName))
if err != nil {
panic(err)
}
DB_INSTANCE = db
return nil
} else {
dbn, err := sql.Open("mysql", fmt.Sprintf("%s:%s#cloudsql(%s)/%s", user, password, connectionName, dbName))
if err != nil {
panic(err)
}
DB_INSTANCE = dbn
return nil
}
What I noticed is that the connection to the Cloudsql instance seems to be established since the above code is not what produces the error, but my test query agains the database.
func TestDatabaseHandler(w http.ResponseWriter, r *http.Request) {
w.WriteHeader(http.StatusOK)
var name string
err := DB_INSTANCE.QueryRow("SELECT name FROM names WHERE id = ?", 1).Scan(&name)
if err != nil {
if err == sql.ErrNoRows {
PrintSingleResponseJson(w, "error", fmt.Sprintf("no rows found"))
} else {
Log(r, fmt.Sprintf("Could not connect to database: %v", err))
PrintSingleResponseJson(w, "error", fmt.Sprintf("could not connect to database: %s", err))
}
return
}
PrintSingleResponseJson(w, "success", fmt.Sprintf("%s", name))
}
I appreciate all help.