Background server gets terminated

sbt
circle.yml

#1
# Scala CircleCI 2.0 configuration file
#
# Check https://circleci.com/docs/2.0/sample-config/ for more details
#
version: 2
jobs:
  build:
    docker:
      # specify the version you desire here
      - image: circleci/openjdk:8-jdk

      # Specify service dependencies here if necessary
      # CircleCI maintains a library of pre-built images
      # documented at https://circleci.com/docs/2.0/circleci-images/
      - image: circleci/postgres:9.6

    working_directory: ~/repo

    environment:
      # Customize the JVM maximum heap limit
      JVM_OPTS: -Xmx3200m
      TERM: dumb

    steps:
      - checkout

      # Download and cache dependencies
      - restore_cache:
          keys:
          - v1-dependencies-{{ checksum "build.sbt" }}
          # fallback to using the latest cache if no exact match is found
          - v1-dependencies-

      - run: ./tools/activator/activator clean compile

      - save_cache:
          paths:
            - ~/.m2
          key: v1-dependencies--{{ checksum "build.sbt" }}

      - run:
          name: Starting server
          command: ./startServerForTests
          background: true

      - run: wget "http://localhost:3333/healthcheck"

      # run tests!
      - run: ./tools/activator/activator test

My config.yml file is above. I got it almost working, but for some reason when I start my server for tests i see the follow error message and then wget always fails since the server is being stopped. How do I ensure the server stays up for the next two run steps?

Listening for transport dt_socket at address: 9999
[info] Loading project definition from /home/circleci/repo/project
[info] Set current project to zently (in build file:/home/circleci/repo/)

--- (Running the application, auto-reloading is enabled) ---

[info] p.c.s.NettyServer - Listening for HTTP on /0.0.0.0:3333

(Server started, use Ctrl+D to stop and go back to the console...)

[info] p.c.s.NettyServer - Stopping server...

#2