Migration fail if it starts before postgres is ready.

[coreyshuman]

Postgres takes a long time start up on some machines (30+ seconds).
In this situation, the migration server will try to run and will crash because Postgres will either not have opened the port yet, or it will send a incomplete startup packet.

Migration server should have a retry mechanism to keep trying until success (or container kill).

[webbrain-one]

Hi! I’ve opened PR #17 for this. It adds a retry mechanism to the migration server so it keeps trying until Postgres is ready, preventing the crash that happens when Postgres takes longer to start.