Unable to connect to "db"

[llcool]

I know that this is an old issue, but db is not defined as a hostname and does not resolve to any IP address.
If I login to the db container then connect to the database, I get....

root@273149152bf5:/# psql postcodesiodb postcodesio
psql (16.4 (Debian 16.4-1.pgdg110+2))
Type "help" for help.

postcodesiodb=# SELECT pg_read_file('/etc/hostname');
 pg_read_file 
--------------
 273149152bf5+
 
(1 row)

postcodesiodb=# \conninfo
You are connected to database "postcodesiodb" as user "postcodesio" via socket in "/var/run/postgresql" at port "5432".
postcodesiodb=# 

postcodesiodb=# SELECT boot_val, reset_val FROM pg_settings WHERE name='listen_addresses';
 boot_val  | reset_val 
-----------+-----------
 localhost | *
(1 row)

[llcool]

This fixes the issue with Unable to connect to "db"
Both containers must run on the same shared network.

services:
  api:
    image: idealpostcodes/postcodes.io:latest
    restart: unless-stopped
    build:
      context: .
      dockerfile: ./Dockerfile
    depends_on:
      - db
    environment:
      - POSTGRES_DATABASE=postcodesiodb
      - POSTGRES_PASSWORD=secret
      - POSTGRES_USER=postcodesio
      - POSTGRES_HOST=db
    networks:
      - postcodes_io
    ports:
      - 8000:8000
  db:
    image: idealpostcodes/postcodes.io.db:latest
    restart: unless-stopped
    environment:
      - POSTGRES_DB=postcodesiodb
      - POSTGRES_PASSWORD=secret
      - POSTGRES_USER=postcodesio
    networks:
      - postcodes_io
networks:
  postcodes_io:
    name: postcodes_io