How to run migrations before application upgrade?

Question

According to Distillery's docs migrations "should be deployed in advance of application upgrades", so far I've made simple upgrades which have not involved too much change of GenServer's state or applying migrations, in fact, I've applied upgrades but I've had to bring down the application and start them again for the release task to apply the migrations successfully. I want to know how can I apply migrations in advance as per the docs say?