travis ci无法识别Mongodb服务

Question

我已根据documentation在{em> .travis.yaml 文件中添加了services: mongodb。

但是当Travis构建系统尝试启动mongo服务时，它complains（第536行）表明：

  

mongod：无法识别的服务

我想念什么？

是我的 .travis.yaml 文件：

language: android
jdk: oraclejdk8

sudo: false

services: mongodb

env:
  global:
    - ANDROID_API=28
    - ANDROID_BUILD_TOOLS=27.0.3

android:
components:
- tools
- platform-tools
- tools
- build-tools-$ANDROID_BUILD_TOOLS
- android-$ANDROID_API
- extra-google-google_play_services
- extra-google-m2repository
- extra-android-m2repository
- addon-google_apis-google-$ANDROID_API
- extra-android-support

licenses:
- android-sdk-preview-license-.+
- android-sdk-license-.+
- google-gdk-license-.+

before_install:
- yes | sdkmanager "platforms;android-27"
- chmod +x gradlew

before_cache:
- rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
- rm -fr $HOME/.gradle/caches/*/plugin-resolution/
cache:
  directories:
  - $HOME/.gradle/caches/
  - $HOME/.gradle/wrapper/
  - $HOME/.android/build-cache

script:
  - mongod --version
  - ./gradlew build check