Docker, mongodb don't connection nodejs

I am facing weird issue while connecting MongoDB running in a separate container from my nodejs container, it displays the following error while trying to connect to MongoDB. My Dockerfile

    FROM node:latest

WORKDIR /usr/src/app

COPY package*.json ./

RUN npm install

COPY . .

EXPOSE 8000

CMD ["npm","start"]
enter code here

docker-compose

version: '3'
services:
  web:
    build: .
    ports:
     - "8000:8000"
    links:
    - mongo
    - redis

  mongo:
    image: mongo
    ports:
      - "49155:49155"
  redis:
    image: "redis:alpine"

mongo config

mongoose: { // MongoDB
    // uri: mongodb://username:password@host:port/database?options
    uri: `mongodb://localhost:27017/${DB_NAME}`,
    options: {
    },
    seed: {
      path: '/api/models/seeds/',
      list: [
        {
          file: 'user.seed',
          schema: 'User',
          plant: 'once' //  once - always - never
        },
        {
          file: 'example.seed',
          schema: 'Example',
          plant: 'once'
        }
      ]
    },
  },

Issue enter image description here

I am only studied docker pls help me