I installed Postgresql 9.4.0 installed on my Mac (10.10.1/Yosemite) using homebrew. It does not work.
I have created the softlink to /usr/local/opt/postgresql/homebr
For posterity, I had this issue and wanted to note what worked for me.
I am running postgres 11.2 on High Sierra. I had recently upgraded from postgres 10 with brew postgresql-upgrade-database.
I kept getting the error psql: could not connect to server: No such file or directory, and my server.log indicated is another postmaster (PID 5894) running in data directory "/usr/local/var/postgres"?
I tried several solutions including restarting my computer, deleting postmaster.pid, using brew services restart postgres, but to no avail. I eventually stumbled on the solution:
brew unlink postgresql && brew link postgresql
No idea why this worked, but putting it here mostly so I can reference it myself in the future! Throw stuff at the wall till it sticks!