Cuando tengas este error con PostgreSQL:
psql: could not connect to server: No such file or directory Is the server running locally and accepting connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
Se resuelve en MAC corriendo los siguientes comandos:
$ pg_ctl -D /usr/local/var/postgres -l /usr/local/var/postgres/server.log start
Si no se arregla te toca reinstalar
$ brew services stop postgresql
$ rm /usr/local/var/postgres/postmaster.pid # adjust path accordingly to your install
$ brew services start postgresql