Ubuntu service - pq: password authentication failed for user "root"

Question

I have an application running on Ubuntu server that's using PostgreSQL.

I can run the application's executable (as a non-root user) from the project's directory.

I have created a service for this application (/etc/systemd/system/cineapi.service), so that it starts automatically on reboot. The contents of this file are:

[Unit]
Description=cineapi

[Service]
Type=simple
Restart=on-failure
RestartSec=5s
WorkingDirectory=/home/saurabh/projects/cineapi
ExecStart=/home/saurabh/projects/cineapi/cineapi.o

[Install]
WantedBy=multi-user.target

When a reload the system daemon and start the service like:

sudo systemctl daemon-reload
sudo service cineapi start

I'm getting an error:

pq: password authentication failed for user "root"

I dont understand why this is happening. I'm not using the "root" user anywhere in the application. It's .env file looks like

postgres://goapi:somepassword@MY_IPV4_ADDR:DB_PORT/cineapi

and is sourced at startup. I also have the following changes in:

• /etc/postgresql/16/main/postgresql.conf

  password_encryption = scram-sha-256
  

• /etc/postgresql/16/main/pg_hba.conf

  host    cineapi         goapi           MY_IPV4_ADDR            scram-sha-256
  

• DB user goapi has superuser privileges

  postgres=# \du
                             List of roles
  Role name |                         Attributes                         
  ----------+------------------------------------------------------------
  goapi     | Superuser, Create DB
  postgres  | Superuser, Create role, Create DB, Replication, Bypass RLS
  

Logs

Postgres logs when executing the binary:

2024-02-24 18:42:31.053 PST [16433] LOG:  checkpoint starting: time
2024-02-24 18:42:36.817 PST [16433] LOG:  checkpoint complete: wrote 60 buffers (0.4%); 0 WAL file(s) added, 0 removed, 0 recycled; write=5.737 s, sync=0.014 s, total=5.765 s; sync files=54, longest=0.003 s, average=0.001 s; distance=201 kB, estimate=201 kB; lsn=0/1A477E0, redo lsn=0/1A477A8
2024-02-24 18:43:39.173 PST [16573] goapi@cineapi LOG:  could not receive data from client: Connection reset by peer             #### ---------------- I stopped the executable ----------------- ####

Postgres logs when starting the application's system service

2024-02-24 18:37:31.024 PST [16432] LOG:  database system is ready to accept connections
2024-02-24 18:38:28.926 PST [16473] root@root FATAL:  role "root" does not exist