Doubts on the applied use of async/await with Angular

Question

Good morning,

Even reading about the concepts and uses of async and of await I’m still having problems with their actual application.

Basically in my ngOnInit call for a function:

ngOnInit() {
    this.authenticateUser();
  }

Function this:

authenticateUser() {

    console.log("----Autenticando Usuário----");

    this.token = localStorage.getItem("token");
    this.userName = localStorage.getItem("userName");
    this.userPhoto = localStorage.getItem("userPhoto");

    this.currentUser = this.auth.getSession(this.token);

    this.attributions = this.currentUser.sessao.grupos;
    this.userEmail = this.currentUser.sessao.email;
    this.instalation = this.currentUser.instalacao;

   }

The problem is that the currentUser gets the value as null in its execution, because its value is set without receiving the correct value of this.auth.getSession(this.token);

This Auth being built from a service RestApiService

constructor(private auth: RestApiService) { }

Having within this service the method getSession() that returns an object JSON containing user information returned by API.

getSession(xtrToken) {
    xtrToken = "{\"token\":\"" + xtrToken.toString() + "\"}";
    this.http.post(this.apiURL + "/auth", xtrToken)
      .subscribe(function (resposta) {
        if (resposta != null) {
          localStorage.setItem("currentUser", JSON.stringify(resposta));
          if (window.location.href.indexOf("?") > -1) {
            var url = window.location.href;
            var value = url = url.slice(0, url.indexOf('?'));
            value = value.replace('@System.Web.Configuration.WebConfigurationManager.AppSettings["BaseURL"]', '');
            var newUrl = value;
            window.history.pushState({}, null, newUrl);
          }
          this.currentUser = JSON.parse(localStorage.getItem("currentUser"));
        }
      });
      return this.currentUser;
  }

I tried to put in that role getSession as async, and on her call something like this:

async authenticateUser() {

    console.log("----Autenticando Usuário----");

    this.token = localStorage.getItem("token");
    this.userName = localStorage.getItem("userName");
    this.userPhoto = localStorage.getItem("userPhoto");

    this.currentUser = await this.auth.getSession(this.token);

    this.attributions = this.currentUser.sessao.grupos;
    this.userEmail = this.currentUser.sessao.email;
    this.instalation = this.currentUser.instalacao;

   }

But it didn’t do any good. Basically what would be the right way to expect the return of API before "set" the value of this.currentUser ?