Here is my code:
import { HttpClient, HttpErrorResponse, HttpHeaders } from \'@angular/common/http\';
To add multiples params or headers you can do the following:
constructor(private _http: HttpClient) {}
//....
const url = `${environment.APP_API}/api/request`;
let headers = new HttpHeaders().set('header1', hvalue1); // create header object
headers = headers.append('header2', hvalue2); // add a new header, creating a new object
headers = headers.append('header3', hvalue3); // add another header
let params = new HttpParams().set('param1', value1); // create params object
params = params.append('param2', value2); // add a new param, creating a new object
params = params.append('param3', value3); // add another param
return this._http.get(url, { headers: headers, params: params })