We can create a file for the postgres user with all the customized settings:

/var/lib/postgresql/.psqlrc:
----------------------------
\set COMP_KEYWORD_CASE upper
\x auto
\pset null --NULL--
\timing

And we can also create that same file for a regular user, in their $HOME directory.

/home/<user>/.psqlrc:
---------------------
\set COMP_KEYWORD_CASE upper
\x auto
\pset null --NULL--
\timing