Mongo restore docker container returns 'error connecting to db server'

Question

I've been searching for an answer to this using this question here as the basis since last night, however I get this error that I can't solve:

Step 4/4 : RUN mongorestore /trapsdump/ --host mongo:27017
---> Running in be3d84e526ab

2018-05-18T10:52:50.575+0000 Failed: error connecting to db server: no reachable servers

I'm using Docker-compose for this. I've used Docker a few times before building containers, but am no expert, however I think everything is correctly configured. I'm using this to seed the database as we have a 'demo' collection stored on mLab.

This is my Dockerfile:

FROM node:9.11.1

RUN mkdir /src

RUN npm install nodemon -g

WORKDIR /src
ADD ./package.json /src/package.json
RUN npm install

COPY . .

EXPOSE 3000

CMD npm start

This is the docker-compose.yml:

version: "2"
services:
  mongo:
    container_name: mongo
    image: mongo
    volumes:
      - ./data:/data/db
    ports:
      - "27017:27017"
      - "11990:11990"

  mongo-seed:
    build: ./mongo-seed
    links:
      - mongo

  app:
    container_name: traps
    restart: always
    build: .
    ports:
      - "3000:3000"
    links:
      - mongo

And this is the mongo-seed/Dockerfile:

FROM mongo

RUN mongodump --uri=mongodb://xxxxxxxxxxxxx@xxxxxxxxxxxx:xxxxx/xxxxxx -o trapsdump
RUN mongorestore /trapsdump/ --host mongo:27017

If pulls down the collection from mLab and dumps it locally.

So if anyone can point out where i'm going wrong, that would be excellent.