Cloudsql readme

[evanj]

Description

Fix incorrect information in the README.md file:
To connect to Cloud SQL, you need to pass the entire "instance name",
which is of the form: project-id:region:instance-name. For example:
my-project:us-central1:my-cloudsql-instance

Checklist

• Code compiles correctly
• Created tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary
• Added myself / the copyright holder to the AUTHORS file

[arnehormann]

Can you link to official docs describing the format? We have to crosscheck, the link to the docs makes it simpler.

[lennrt]

@arnehormann It looks like the official docs are still outdated. I am having an issue with the connection string as well, as are other people.

[evanj]

@lrudolph1 thanks for looking up a reference. I think the following effectively mentions this:

From https://cloud.google.com/sql/docs/external#go

Connection statement:

const dsn = "root@unix(/cloudsql/<INSTANCE_CONNECTION_NAME>)/"
db, err := sql.Open("mysql", dsn)

The Cloud SQL proxy docs say: https://cloud.google.com/sql/docs/external#6_start_the_proxy

1. Copy your instance connection name from the Instance details page.

I'm going to update this pull request accordingly. Thanks!

[evanj]

I included a link, but the documentation I linked to isn't super helpful. I reported a documentation bug to Google but don't hold your breath. I still think including an example would be consistent with all the other examples, and very useful given that Google's official documentation is actually either incorrect or missing an example like this.