1. Locate your Postgres data directory (e.g., /opt/postgres/data) and check your pg_hba.conf

2. Find an entry like the following:
# TYPE  DATABASE        USER            ADDRESS                 METHOD
# ...
# IPv4 local connections:
host    all             all             127.0.0.1/32            trust

3. add new ones like follows (BEFORE the line shown above):
host 	cashdb		cashu99		127.0.0.1/32		password
host 	all		cashu99		127.0.0.1/32		reject

4. reload the authentication file:
pg_ctl -D /opt/postgres/data reload

5. now try to login to cashdb as user cashu99
psql -h 127.0.0.1 cashdb cashu99

6. logout and try to log in to database postgres
psql -h 127.0.0.1 postgres cashu99