title: Vue proxy setting does not work
body: <p>I have a Vue project from <code>@vue/cli</code> 3.x.</p>
  
  <p>The proxy I defined in <code>package.json</code> based on <a href="https://alligator.io/vuejs/using-new-vue-cli-3/#proxy" rel="noreferrer">this article</a> is not working. The destination server doesn't see the API request.</p>
  
  <p>What am I missing here?</p>
  
  <p>The vue file:</p>
  
  <pre><code>&lt;script lang="ts"&gt;
  import { Component, Prop, Vue } from 'vue-property-decorator';
  import VueResource from 'vue-resource';
  
  Vue.use(VueResource);
  
  @Component
  export default class HelloWorld extends Vue {
    @Prop() private msg!: string;
  
    constructor() {
      super();
  
      this.$http.post('/api');
    }
  }
  &lt;/script&gt;
  </code></pre>
  
  <p>package.json:</p>
  
  <pre><code>  "proxy": {
      "/api": "http://localhost:9000/api"
    },
  </code></pre>