Migration-assist from binary install to docker install

Summary
Trying to migrate a Mattermost installation on a Debian server to a docker container on the same server

I have a old Mattermost instance running on a debian server, which use a mariadb database. Since I want to run other services on that server, I went to the docker version. The old instance work, and the new one too. Now, I would like to transfer everything from the first instance to the new, docker one. Since the old instance run on Mysql, I follow the guide here : Automated PostgreSQL migration - Mattermost documentation to migrate the database to postgresql. I get stuck on the following command.

Steps to reproduce
migration-assist postgres 'postgres://username:password@Container_IP:5432/mattermost' --run-migration --mattermost-version='9.11.6'

Expected behavior
I would expect the command to work

Observed behavior
I get the following error: An Error Occurred: failed to grab connection to the database: pq: SSL is not enabled on the server.

Well, I just had to put ?sslmode=disable at the end of the url. How can I change this post to resolve?