How do I fix stale postmaster.pid file on Postgres?

The problem is that the postmaster.pid file needs to be removed manually and regenerated by postgres, and these are the steps to do it. (Keep in mind the version might change, var-12, might be var-13 etc)

1. Open your terminal, and cd into the postgres directory: cd /Users/<user_name>/Library/Application\ Support/Postgres
2. Make sure you're in the right place, ls you should see something like var-12 or var-<version #>
3. Verify the file is there, ls var-12 (keep in mind the var-XX is equivalent to your PGSQL version)
4. Verify the Postgres server is not running by viewing desktop app

Version might change so could be var-12, var-13, etc etc depending on age of this article.

Library/Application Support/Postgres➜ ls var-12PG_VERSION           pg_hba.conf          pg_replslot          pg_subtrans          postgresql.auto.confbase                 pg_ident.conf        pg_serial            pg_tblspc            postgresql.confglobal               pg_logical           pg_snapshots         pg_twophase          postgresql.logpg_commit_ts         pg_multixact         pg_stat              pg_wal               postmaster.optspg_dynshmem          pg_notify            pg_stat_tmp          pg_xact              postmaster.pid <----

1. Then remove postmaster.pid, rm var-12/postmaster.pid
2. or rm var-<PG version #>/postmaster.pid
3. Go back to your console, start your postgres server, and it should be functioning again, and you should have full access to your schemas.

In my case I used the code rm var-13/postmaster.pid and solved.