Restclient.post Angular 7

Question

I’m trying to create a post like this, more in angular 7:

    get '/callback' do
  # get temporary GitHub code...
  session_code = request.env['rack.request.query_hash']['code']

  # ... and POST it back to GitHub
  result = RestClient.post('https://github.com/login/oauth/access_token',
                          {:client_id => CLIENT_ID,
                           :client_secret => CLIENT_SECRET,
                           :code => session_code},
                           :accept => :json)

  # extract the token and granted scopes
  access_token = JSON.parse(result)['access_token']
end

This way:

getClient(session_code: any) {
    this.http.post("https://github.com/login/oauth/access_token", {
      "client_id": this.CLIENT_ID,
      "client_secret": this.CLIENT_SECRET,
      "code": session_code
    }, httpOptions).subscribe(
      data => {
        console.log("POST Request is successful ", data);
      },
      error => {
        console.log("Error", error);
      }
    );
  }

But this giving error

I’m creating this angular authentication, I found nothing researching: https://developer.github.com/v3/guides/basics-of-authentication/