For 9.6, I did the following:
steps:
- run: echo 'deb http://apt.postgresql.org/pub/repos/apt/ jessie-pgdg main' | sudo tee /etc/apt/sources.list.d/pgdg.list > /dev/null
- run: wget --no-check-certificate -q https://www.postgresql.org/media/keys/ACCC4CF8.asc -O- | sudo -u root apt-key add -
- run: sudo apt-get update
- run: sudo apt-get install postgresql-9.6 postgresql-client-9.6