无法使用Angular 5应用程序从启用CORS的API获取响应

我想从Angular 5应用程序调用Watson对话API,为此,我使用Angular HttpClient。

import { HttpClient, HttpHeaders } from '@angular/common/http';
const url = 'https://gateway.watsonplatform.net/conversation/api?version=2017-05-26';
const username = 'my-username';
const password = 'secret';
const headers = new HttpHeaders({
  Authorization: 'Basic ' + btoa(`${username}:${password}`)
});
this.httpClient.get('https://gateway.watsonplatform.net/conversation/api?version=2017-05-26', { headers: headers })
  .subscribe(res => {
    console.log(res);
  });

它应该调用API并返回响应,但返回以下错误:

Failed to load https://gateway.watsonplatform.net/conversation/api?version=2017-05-26: Request header field Authorization is not allowed by Access-Control-Allow-Headers in preflight response.

该请求与Postman和Node完美配合。js请求包,但不适用于Angular 5应用程序。

样本卷曲请求:

curl -u "{username}":"{password}" "https://gateway.watsonplatform.net/conversation/api/v1/{method}"

如果我添加以下内容,上述请求可以正常工作 Allow-Control-Allow-Origin: * chrome中的扩展,因此无法理解Angular应用程序有什么问题。

提前谢谢。