psql connection to postgis db in docker -failing all though db is running and accessible

Question

After installing https://github.com/qwc-services/qwc-docker I am not able to connect to the postgis db that's created. I see the following

f89d540947ca sourcepole/qwc-demo-db:v2022.09.03
"docker-entrypoint.s…" 43 hours ago Up 43 hours (healthy)
127.0.0.1:5439->5432/tcp qwc-docker_qwc-postgis_1 c94f41f33567 sourcepole/qwc-qgis-server:3.22-odbc
"/sbin/my_init" 43 hours ago Up 3 hours
127.0.0.1:8001->80/tcp qwc-docker_qwc-qgis-server_1

I have tried the following and got errors

psql -h 127.0.0.1 -p 5439 -U qwc_service -d qwc-demo
Password for user qwc_service: 
psql: error: connection to server at "127.0.0.1", port 5439 failed: FATAL:  database "qwc-demo" does not exist

and also

docker exec f89d540947ca psql -U qwc_service -c "\l"
psql: error: connection to server on socket "/var/run/postgresql/.s.PGSQL.5432" failed: FATAL:  database "qwc_service" does not exist

all db, users, passwords are as per the link above.

I see the following DB's are available

docker exec -it f89d540947ca psql -U postgres
psql (13.8 (Debian 13.8-1.pgdg110+1))
Type "help" for help.

postgres=# \l
                                 List of databases
   Name    |  Owner   | Encoding |  Collate   |   Ctype    |   Access privileges   
-----------+----------+----------+------------+------------+-----------------------
 postgres  | postgres | UTF8     | en_US.utf8 | en_US.utf8 | 
 qwc_demo  | postgres | UTF8     | en_US.utf8 | en_US.utf8 | 
 template0 | postgres | UTF8     | en_US.utf8 | en_US.utf8 | =c/postgres          +
           |          |          |            |            | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.utf8 | en_US.utf8 | =c/postgres          +
           |          |          |            |            | postgres=CTc/postgres
(4 rows)

Running - Ubuntu 20.10