Dockerized Node App unable to connect to Dockerized Postgres Database – Debian

I have tried many possible solutions to it, Not able to make any of them work.
Here it goes:

I built a nodejs container and a postgres docker container. Used docker compose to configure them both and used Dockerfile to build the nodejs/typescript application.

docker-compose.yml

version: "3"

volumes: 
  pg_vol:

networks:
  app-network:
    driver: bridge

services:
  db:
    container_name: db
    image: postgres
    ports:
      - "5432:5432"
    environment:
      - POSTGRES_DB=db22
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=q123
    volumes:
      - pg_vol:/var/lib/postgresql/data
    networks:
      - app-network
  webapp:
    container_name: webapp
    build:
      context: ./
      dockerfile: Dockerfile
    environment:
      - DATABASE_URL=postgres://postgres:q123@db:5432/db22
    ports:
      - "5000:5000"
    networks: 
      - app-network
    depends_on:
      - db

Dockerfile

FROM node:14
WORKDIR /usr/src/app
COPY package*.json ./
RUN npm install
COPY ./dist .
CMD [ "npm", "start" ]

When I do docker-compose up --build, it shows an error while connecting to the postgres db. DB starts alright.

Error STDOUT

Starting db ... done
Starting webapp ... done
Attaching to db, webapp
db        | 
db        | PostgreSQL Database directory appears to contain a database; Skipping initialization
db        | 
db        | 2020-11-24 16:32:25.918 UTC [1] LOG:  starting PostgreSQL 13.1 (Debian 13.1-1.pgdg100+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 8.3.0-6) 8.3.0, 64-bit
db        | 2020-11-24 16:32:25.918 UTC [1] LOG:  listening on IPv4 address "0.0.0.0", port 5432
db        | 2020-11-24 16:32:25.918 UTC [1] LOG:  listening on IPv6 address "::", port 5432
db        | 2020-11-24 16:32:25.923 UTC [1] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
db        | 2020-11-24 16:32:25.928 UTC [25] LOG:  database system was shut down at 2020-11-24 16:32:18 UTC
db        | 2020-11-24 16:32:25.933 UTC [1] LOG:  database system is ready to accept connections
webapp    | 
webapp    | > [email protected] start /usr/src/app
webapp    | > node app.js
webapp    | 
webapp    | undefined
webapp    | undefined
webapp    | running in-code config
webapp    | Error: connect EHOSTUNREACH 172.19.0.2:5432
webapp    |     at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1146:16) {
webapp    |   errno: -113,
webapp    |   code: 'EHOSTUNREACH',
webapp    |   syscall: 'connect',
webapp    |   address: '172.19.0.2',
webapp    |   port: 5432
webapp    | }
webapp    | npm ERR! code ELIFECYCLE
webapp    | npm ERR! errno 1
webapp    | npm ERR! [email protected] start: `node app.js`
webapp    | npm ERR! Exit status 1
webapp    | npm ERR! 
webapp    | npm ERR! Failed at the [email protected] start script.
webapp    | npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
webapp    | 
webapp    | npm ERR! A complete log of this run can be found in:
webapp    | npm ERR!     /root/.npm/_logs/2020-11-24T16_32_26_955Z-debug.log
webapp exited with code 1

Please help with correcting me.

System:

Fedora 33 (Workstation Edition)

EDIT:
I restarted the docker container with command docker start webapp. Same error as above.