如何在Vue CLI 4中加载环境变量

Question

我想在我的Vue.js应用程序中使用环境变量。由于我正在使用Vue cli 4，因此无需安装dotenv或其他任何工具就可以做到这一点。我的根目录中有一个.env文件，但是当我尝试console.log一个未定义的环境变量时，我在做什么错以及如何使用它们？这是我的package.json：

{
  "name": "frontend",
  "version": "0.1.0",
  "private": true,
  "scripts": {
    "serve": "vue-cli-service serve",
    "build": "vue-cli-service build",
    "lint": "vue-cli-service lint"
  },
  "dependencies": {
    "core-js": "^3.6.5",
    "firebase": "^8.0.0",
    "vue": "^2.6.11",
    "vue-router": "^3.4.8",
    "vuex": "^3.5.1"
  },
  "devDependencies": {
    "@vue/cli-plugin-babel": "~4.5.0",
    "@vue/cli-plugin-eslint": "~4.5.0",
    "@vue/cli-service": "~4.5.0",
    "babel-eslint": "^10.1.0",
    "eslint": "^6.7.2",
    "eslint-plugin-vue": "^6.2.2",
    "node-sass": "^4.12.0",
    "sass-loader": "^8.0.2",
    "vue-template-compiler": "^2.6.11"
  },
  "eslintConfig": {
    "root": true,
    "env": {
      "node": true
    },
    "extends": [
      "plugin:vue/essential",
      "eslint:recommended"
    ],
    "parserOptions": {
      "parser": "babel-eslint"
    },
    "rules": {}
  },
  "browserslist": [
    "> 1%",
    "last 2 versions",
    "not dead"
  ]
}

我的.env文件位于项目根目录中：

VUE_APPT_TEST=test

和我的console.log：

 created() {
      console.log(process.env.VUE_APPT_TEST)
  }