While it it is not recommended (the very first sentence from the GET method's documentation), technically you could do it:

  constructor(private http: HttpClient) {}

  doAGetWithBodyRequest(): void {
    this.http.request(
    // the type of request:
    'get',
    // the path:
    'https://localhost:8080',
    // the body:
    { body: 'your-body-in-here' }
  }