Issue in Native HTTP with POST request in iOS

I am trying POST request using native HTTP in iOS but its not working.
GET with both angular http and native http working perfect but POST with angular and native http not working.

My Ionic Info:
Ionic:

ionic (Ionic CLI) : 4.10.3 (/usr/local/lib/node_modules/ionic)
Ionic Framework : @ionic/angular 4.1.1
@angular-devkit/build-angular : 0.13.5
@angular-devkit/schematics : 7.2.4
@angular/cli : 7.3.5
@ionic/angular-toolkit : 1.4.0

Cordova:

cordova (Cordova CLI) : 8.1.2 (cordova-lib@8.1.1)
Cordova Platforms : android 7.1.4, ios 4.5.5
Cordova Plugins : cordova-plugin-ionic-keyboard 2.1.3, cordova-plugin-ionic-webview 3.1.2, (and 8 other plugins)

System:

ios-deploy : 1.9.4
ios-sim : 8.0.0
NodeJS : v10.15.3 (/usr/local/bin/node)
npm : 6.4.1
OS : macOS High Sierra
Xcode : Xcode 10.1 Build version 10B61


Code for POST request in iOS

import { HTTP } from ‘@ionic-native/http/ngx’;

const httpOptions = {
headers: new HttpHeaders({
‘Authorization’: Authorization,
‘Content-type’ : ‘application/json’,
})
};

const body = new HttpParams()
.set(‘grant_type’, ‘authorization_code’)
.set(‘client_id’ , this.client_id)
.set(‘redirect_uri’, this.redirect_url)
.set(‘code’,code);

this.http.post(this.token_url, body,httpOptions)
.then(data => {
console.log(’–token res–’+JSON.stringify(data));
})
.catch(error => {
console.log(’–token err–’+JSON.stringify(error));
});

can anybody help me out here.