Nuxt/Vue CORS error on change page, with asyncData

Question

I have an error on my Nuxt App and I don't understand why it not work. I have 2 files post_data.json and 0001.json in my server. The post_data.json work without any CORS issue, this is the index.vue page fetch :

  async fetch() {

    const type = 'post';

    await this.$store.dispatch('getPostBy',type).then(()=> {
        console.log("Got some data, now lets show something in this component")
    }, error => {
        console.error("Got nothing from server. Prompt user to check internet connection and try again", error)
    })  
  },

in store :

 async getPostBy ({ commit, state}, type) {
        try {
          let siteUrl = state.api_url;
          let url = `${siteUrl}/${type}/${type}_list.json`;
    
          const headers = {
              "Content-Type": "application/json",
              "Accept": "application/json",
          };
    
          await fetch(url, {
              method: "GET",
              headers,
          })
          .then(data => data.json())
          .then(response=>{
              commit('SET_POSTS', response) // Save Item in Store
          })
          .catch( e=> {
              console.log("getPostBy 3. OUTSIDE 401 ", e);
          });
    
        } catch (e) {
        }
      },

Instead, when I navigate to single post, i get this error :

Access to fetch at 'http://www.example.com/post/0001.json' from origin 'http://localhost:8010' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

This is the code of asyncData :

   asyncData({app, route, store}) {
    const id = route.query.p;
    const category = 'post';

try {

  let siteUrl = 'http://www.example.com';
  let url = `${siteUrl}/${category}/${id}.json`;


  const headers = {
      "Access-Control-Allow-Origin": "*",
      "Content-Type": "application/json",
      "Accept": "application/json",
  };

   fetch(url, {
      method: "GET",
      //mode: "no-cors",
      headers,
  })
  .then(data => data.json())
  .then(response=>{
    console.log("response", response)   
    let item = response;
    
    store.dispatch("updateItem", {item})

  })
  .catch( e=> {
      console.log("asyncData error ", e);
  });

} catch (e) {
}

},

If i open the file in browser or if I reload the page, i will see the content of json file, instead if I change route I get the CORS error. I tryed to add "Access-Control-Allow-Origin": "*" and also mode: "no-cors", but i still have the issue.