我的API具有以下CORS設置：（我是所有者，我可以更改這些設置）中間件功能：// HeaderMiddleware ...func HeaderMiddleware(next httprouter.Handle) httprouter.Handle {    return httprouter.Handle(func(w http.ResponseWriter, r *http.Request, p httprouter.Params) {        w.Header().Set("Content-Type", "application/json")        w.Header().Set("Access-Control-Allow-Origin", "*")        w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept, X-APIKEY")        // ! Production        // if r.Header.Get("X-APIKEY") != "fdfdsf5df6d541cd6" || r.RemoteAddr != frontendURL {        //  w.WriteHeader(http.StatusForbidden)        //  json.NewEncoder(w).Encode(NoContentResponse{Success: false, Error: "You aren't allowed to request the api here."})        //  return        // }        // ! Production        next(w, r, p)    })}X-APIKEY 標頭還不是必需的，沒有它的請求也可以正常工作：fetch('http://localhost:8013/[email protected]/usage', { headers: { } }).then(response => response.json()).then(console.log)返回{used: false}（預期響應）但是，如果我添加 X-APIKEY 標頭：fetch('http://localhost:8013/[email protected]/usage', { headers: { 'X-APIKEY': 'sdfsdfsafsf' } }).then(response => response.json()).then(console.log)拋出以下錯誤：Access to fetch at 'http://localhost:8013/[email protected]/usage' from origin 'http://localhost:8080' 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.如果我在 Postman 中使用 X-APIKEY 標頭執行請求，它表示 Access-Control-Allow-Origin 標頭已一起發送： PS： 我已經嘗試過其他標頭，它有效！如果我使用 chrome 發出請求（沒有 X-APIKEY 標頭），則會發送 Access-Control-Allow-Origin 標頭。 感謝您的幫助！