The snap packages for 9.3.15, 9.4.10, 9.5.5 and 9.6.1 are now available. To install them:
sudo snap install postgresql$version
Where $version is one of 93, 94, 95 or 96.
The snap packages for PostgreSQL are a community project being lead by Command Prompt. You can visit the repo at github.
To learn more about snap packages please visit the Ubuntu snapcraft developer FAQ.