title: Ionic - HTTP POST Request not working in iOS, but working in Android and Web
body: <p>I am trying send a push notification via post request in Ionic using HttpClient. It's working in Android and Web, but in iOS show this error:</p>
  
  <pre><code>{"headers":{"normalizedNames":{},"lazyUpdate":null,"headers":{}},"status":0,"statusText":"Unknown Error","url":"https://fcm.googleapis.com/fcm/send","ok":false,"name":"HttpErrorResponse","message":"Http failure response for https://fcm.googleapis.com/fcm/send: 0 Unknown Error","error":{"isTrusted":true}}
  </code></pre>
  
  <p>This is my function:</p>
  
  <pre><code> import {HttpClient, HttpHeaders} from "@angular/common/http";
  
   ...
  
   public sendPost(){
      let url = 'https://fcm.googleapis.com/fcm/send';
      let appKEY = 'key=my_key';
      let body =  {
        "condition":"'topico' in topics",
        "notification" : {
          "title": "Test",
          "body": "Hello!!!",
          "sound": "default"
        }
      }
      let header: HttpHeaders = new HttpHeaders();
      header = header.set('Authorization', appKEY);
      header = header.append("Content-Type", "application/json");
      const options = {
        headers: header
      }
      this.http.post(url, body, options)
      .subscribe(data =&gt; {
        alert("Success!!");
        console.log(data);
      }, error =&gt; {
        alert("Error!");
        console.log(error);
      });
    }
  </code></pre>
  
  <p>My infos</p>
  
  <pre><code>Ionic:
  
     Ionic CLI                     : 5.4.16
     Ionic Framework               : @ionic/angular 4.11.10
     @angular-devkit/build-angular : 0.900.6
     @angular-devkit/schematics    : 9.0.6
     @angular/cli                  : 9.0.6
     @ionic/angular-toolkit        : 2.0.0
  
  Capacitor:
  
     Capacitor CLI   : 1.4.0
     @capacitor/core : 1.5.0
  
  Cordova:
  
     Cordova CLI       : 9.0.0 (cordova-lib@9.0.1)
     Cordova Platforms : none
     Cordova Plugins   : no whitelisted plugins (0 plugins total)
  
  Utility:
  
     cordova-res : 0.10.0
     native-run  : not installed
  
  System:
  
     NodeJS : v12.16.1 (/usr/local/bin/node)
     npm    : 6.13.4
     OS     : macOS Catalina
     Xcode  : Xcode 11.3.1 Build version 11C504
  
  </code></pre>
  
  <p>That happens only with this url, I alread has tested with two others simple urls (without headers) and the post was succefull.</p>