node-gcm: send PushNotification for all device

I am trying to build PushNotification sever using node.js, I used "node-fcm" but it is not work with me, so i tryed to use "node-gcm", but I faced same problem, I don't know how to send notifcation for all users? what I need to write in fild (to:)??

this is my code:

var gcm = require('node-gcm');
var Sender_ID = '55*****';
var API_KEY = 'my server key';
var sender = new gcm.Sender(API_KEY,{'proxy':'http://username:password@my_proxyinternet.com:8080' , timeout: 5000});
var message = new gcm.Message({

    notification: {
        title: "Hello, World",
        icon: "ic_launcher",
        body: "This is a notification that will be displayed."
    }
 });

   var registrationTokens = [];
registrationTokens.push(['All']); 
sender.send(message, { registrationTokens: 'All' }, function (err, response) {
if (err) console.error(err + '  ERROR');
else console.log(response + '  ELSE');

});`

the result is:

{ multicast_id: -1, success: 0, failure: 1, canonical_ids: 0, results: [ { error: 'InvalidRegistration' } ] } Error: Recipient key 'registrationTokens' was provided as an incorrect type. ERROR

Process finished with exit code 0

note: i use Ionic 2 and i can recive notifcation from https://console.firebase.google.com/ .

via ajd.nas