Docker ✖️　Ruby on Railsの開発環境構築でブラウザ表示が出来ない

##現状
localhost:3000にアクセスできない。

##開発環境
macOS High Sierra
ruby 2.6.0p0 (2018-12-25 revision 66547) [x86_64-darwin17]
Bundler version 2.0.1

##構築手順
###1. Dockerのインストール(https://docs.docker.com/docker-for-mac/install/)
###2. RubyとMySQLのDockerイメージをダウンロード

$ docker pull mysql:5.7
$ docker pull ruby:2.6.0

###3. Dockerfile作成

FROM ruby:2.6.0
ENV LANG C.UTF-8
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev nodejs
RUN gem install bundler
WORKDIR /tmp
ADD Gemfile Gemfile
ADD Gemfile.lock Gemfile.lock
RUN bundle install
ENV APP_HOME /first-web-app
RUN mkdir -p $APP_HOME
WORKDIR $APP_HOME
ADD . $APP_HOME

###4. Gemfile作成

source 'https://rubygems.org'
gem 'rails'

###5. 空のGemfile.lock作成

$ touch Gemfile.lock

###6. docker-compose.yml作成

version: '2'
services:
  web:
    build: .
    command: bundle exec rails s -p 3000 -b '0.0.0.0'
    volumes:
      - .:/app_name
    ports:
      - "3000:3000"
    depends_on:
      - db
  db:
    image: mysql:5.7
    environment:
      - MYSQL_ROOT_PASSWORD=password

###7. コンテナにRailsアプリ作成

$ docker-compose run web rails new . --force --database=mysql --skip-bundle

###8. Gemfileの変更

ruby
1# 追記 or コメントアウト
2gem 'therubyracer', platforms: :ruby

###9. build

$ docker-compose build

###10. database.ymlの設定

default: &default
  adapter: mysql2
  encoding: utf8
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  username: root
  password: password
  host: db
development:
  <<: *default
  database: first-web-app_development
test:
  <<: *default
  database: first-web-app_test
production:
  <<: *default
  database: first-web-app_production
  username: first-web-app
  password: <%= ENV['FIRST-WEB-APP_DATABASE_PASSWORD'] %>

###11. コンテナの実行

$ docker-compose up

###12. ブラウザ確認

##ログ

$ docker-compose up
Starting first-web-app_db_1 ... done
Recreating first-web-app_web_1 ... done
Attaching to first-web-app_db_1, first-web-app_web_1
db_1   | 2019-01-17T00:51:49.477568Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
db_1   | 2019-01-17T00:51:49.478825Z 0 [Note] mysqld (mysqld 5.7.24) starting as process 1 ...
・
・
・
web_1  | A server is already running. Check /first-web-app/tmp/pids/server.pid.
web_1  | => Booting Puma
web_1  | => Rails 5.2.2 application starting in development 
web_1  | => Run `rails server -h` for more startup options
web_1  | Exiting
first-web-app_web_1 exited with code 1

##質問