Lost connection error when trying to connect to proxy SQL on VM with Container Optimised OS

For a project with Data Fusion I need to create a Virtual Machine with Proxy SQL. In order to test this proxy I’ve created a second instance with MariaBD but I’m not able to establish the connection with the proxy. Here is what I have:

A VM running on Container Optimised OS with a static internal IP and no external IP. This VM is running with the following startup script:

sudo docker run -d 
  gcr.io/cloudsql-docker/gce-proxy:latest /cloud_sql_proxy 

a Cloud SQL for MySQL instance with private IP activated.

Everything is on the same region and network (default). Firewall are widely open for testing purpose.

When running the following command mysql -u user_name -p'123' -h -P 3307 from a second VM for testing purpose I have the following error:

(HY000): Lost connection to MySQL server at 'handshake: reading initial communication packet', system error: 11 

So what is the issue here?

Source: Docker Questions