最后，我可以设法通过以下方式进行这项工作：

---
image: node:alpine
cache:
  key: ${CI_COMMIT_REF_SLUG}
  paths:
    - ~/.npm
    - .jest
stages:
  - test
  - deploy
before_script:
  - npm ci
  - ANDROID_GOOGLE_MAPS_API_KEY=${CI_COMMIT_BRANCH}_EXPO_ANDROID_GOOGLE_API_KEY
  - IOS_GOOGLE_MAPS_API_KEY=${CI_COMMIT_BRANCH}_EXPO_IOS_GOOGLE_API_KEY
  - export android=$( eval echo \$$ANDROID_GOOGLE_MAPS_API_KEY )
  - export ios=$( eval echo \$$IOS_GOOGLE_MAPS_API_KEY )
jest-tests:
  stage: test
  script:
    - npx jest --ci --passWithNoTests
expo-deployments:
  stage: deploy
  script:
    - echo "EXPO_ANDROID_GOOGLE_API_KEY=$android" >> .env
    - echo "EXPO_IOS_GOOGLE_API_KEY=$ios" >> .env
    - apk add --no-cache bash
    - npx expo login -u $EXPO_USERNAME -p $EXPO_PASSWORD
    - npx expo build:android --release-channel staging --non-interactive

在哪里...

 ...CI_COMMIT_BRANCH is development|staging|production depending which branch in gitlab I am using.
 ...development_EXPO_ANDROID_GOOGLE_API_KEY | staging_EXPO_ANDROID_GOOGLE_API_KEY | production_EXPO_ANDROID_GOOGLE_API_KEY are variables that are stored at the Gitlab project.
 ... I am generating the .env file every time I run the script and saving there my variables with the respective value with: echo "EXPO_ANDROID_GOOGLE_API_KEY=$android" >> .env.

这样，我不需要将.env文件推送到Gitlab中。我只需要在Gitlab的项目设置中定义变量。

希望对别人有帮助！