Connect to a local PostgreSQL database from a docker-compose service

Question

Context

I need to connect from inside a compose service to a PostgreSQL (10) database which is on my local host machine (Ubuntu 18.04).

Description of the errors

I have set service > app > build > to network: host in my compose file:

version: '3.8'
  app:
    image: myservice:0.0.1
    restart: unless-stopped
    build:
      context: .
      dockerfile: Dockerfile
      network: host

The Dockerfile is build FROM python:3.9.1-slim-buster.

Then, from inside my compose service (docker exec -it composefilefolder_app_1 bash) I try to connect to a PostgreSQL database on the host machine with psycopg2 (after having started python):

import psycopg2 

DBPARAMS = {
    'user': 'postgres',
    'password': 'password',
    'host': 'localhost',
    'port': '5432',
    'dbname': 'mydatabase'
}

conn = psycopg2.connect(**DBPARAMS)

but this returns:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.9/site-packages/psycopg2/__init__.py", line 127, in connect
    conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
psycopg2.OperationalError: could not connect to server: Connection refused
    Is the server running on host "localhost" (127.0.0.1) and accepting
    TCP/IP connections on port 5432?
could not connect to server: Cannot assign requested address
    Is the server running on host "localhost" (::1) and accepting
    TCP/IP connections on port 5432?

Then I tried to use my host machine IP (given by ifconfig):

import psycopg2 

DBPARAMS = {
    'user': 'postgres',
    'password': 'password',
    'host': '192.168.x.1',
    'port': '5432',
    'dbname': 'mydatabase'
}

conn = psycopg2.connect(**DBPARAMS)

but now I got a time-out after one minute:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.9/site-packages/psycopg2/__init__.py", line 127, in connect
    conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
psycopg2.OperationalError: could not connect to server: Connection timed out
    Is the server running on host "192.168.x.1" and accepting
    TCP/IP connections on port 5432?

All other parameters are correct as I can connect to this database by running the same command from the host machine directly.

Question

How can I connect to my host machine PostgreSQL database from my compose service?

What else I've tried

1. This thread seemed promising but it doesn't work either.
2. And this one is for Mac users.
3. I also tried to set list_adressess='*' in my local machine postgres.conf file AND to set host all all 0.0.0.0/0 md5 into the pg_hba.conf file without any changes. But if I can avoid to tweak my local PostgreSQL config that would be great.
4. This thread also did not help as it makes use of my local machine IP, for which the connection is timing-out as I said.