Unable to use Postgres DB in docker-compose

I have a Node.js app and have set up docker-compose. I'm trying to use Postgres DB in the container.

Here is docker-compose

version: "3"
services:
  web:
    build: .
    ports:
      - "3000:3000"
    links:
      - redis
      - db
  angular: # image of nginx
    image: "qp-angular-nginx"
    ports:
      - "4200:80" # specify port forewarding

  redis:
    image: "redis:3"
    ports:
     - "6379:6379"     
  db:
    image: "postgres:9.6"
    ports:
     - "5432:5432"
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: postgres
    volumes:
         - pgdata:/var/lib/postgresql/data         
  dbadmin:
    image: "myimage/phppgadmin"
    ports:
         - "8085:80"
    environment:
        POSTGRES_HOST: db
        POSTGRES_PORT: 5432
volumes: 
     pgdata:

I have the containers running successfully and even database connected, but I get this error when making a DB request

 "stack": {
        "code": "ECONNREFUSED",
        "errno": "ECONNREFUSED",
        "syscall": "connect",
        "address": "127.0.0.1",
        "port": 5432
    }