title: Angular 5 : Property 'then' does not exist on type 'Observable<any>'
body: <p>I got this error message "[ts] Property 'then' does not exist on type 'Observable'.", how to solve it?</p>
  
  <p>This is my Component :</p>
  
  <pre><code>  getUsers(){
      this.authService.getUsers().then((res) =&gt; {
        this.user = res;
        console.log(this.user);
      },(err) =&gt; {
        console.log(err);
      });
    }
  </code></pre>
  
  <p>This is my Service :</p>
  
  <pre><code> getUsers(){
      let headers = new Headers();
      headers.append('Content-Type', 'application/json');
      return this.http.get('http://192.168.100.6:3000/users/data-tracer', {headers: headers})
      .map(res =&gt; res.json());
    }
  </code></pre>