HTTP请求头映射为空

我正在尝试向API发送HTTP请求,而API确实需要特定的头才能工作。

直到现在,我尝试了一些不同的方法来发送头。起初,我试图在httpoptions对象中设置头并将其传递给我的'httpclient.get()'函数,但这不起作用。

因为我对angular和typescript非常陌生,所以我读了一些关于如何发送HTTP请求的文章。拦截器应该是我正确的选择,我修改了我的代码。

以下是我提出请求的功能:

constructor(private http: HttpClient) {}

public getVersions() {
    let url = baseUrl + '/docs/versions';

    this.http
        .get(url)
        .subscribe(data =>{
            console.log(data);
        }, err => {
            console.log(err);
        });

    return true;
}

音符: return true; 这里只是测试用的吗

这是我的拦截器

import { Injectable } from '@angular/core';
import { HttpInterceptor, HttpHeaders, HttpHandler, HttpRequest, HttpEvent, HttpResponse }
    from '@angular/common/http';

import { Observable } from 'rxjs';
import 'rxjs';

@Injectable()
export class MyHttpInterceptor implements HttpInterceptor {
    intercept(
        req: HttpRequest<any>,
        next: HttpHandler
    ): Observable<HttpEvent<any>> {

        console.log('intercept http request');
        const duplicate = req.clone({
            headers: new HttpHeaders().set('dummy-header', 'dummy-header-info')
        });

        console.log(duplicate.headers.get('dummy-header');
        console.log('new header request');

        return next.handle(duplicate);
    }
}

这是我的控制台日志

intercept http request
http-interceptor.ts:19 dummy-header-info
http-interceptor.ts:20 new header request
zone.js:2969 OPTIONS http://192.168.111.106:8089/docs/versions 0 ()
api.service.ts:21 
HttpErrorResponse {headers: HttpHeaders, status: 0, statusText: "Unknown Error", url: null, ok: false, …}
error : ProgressEvent {isTrusted: true, lengthComputable: false, loaded: 0, total: 0, type: "error", …}
headers : HttpHeaders {normalizedNames: Map(0), lazyUpdate: null, headers: Map(0)}
message : "Http failure response for (unknown url): 0 Unknown Error"
name : "HttpErrorResponse"
ok : false
status : 0
statusText : "Unknown Error"
url : null
__proto__ : HttpResponseBase

由于缺少请求头,请求失败。 所以对我来说,标题映射看起来是一个空映射。但为什么,我的错误在哪里?