title: Send notification to one user with firebase cloud function node
body: <p>I am trying to send a notification to a specific user using FCM, but I haven't found a way. I have a mobile app and a node server running.</p>
  <p>I want to be able to send a notification when the shipment status changes. I have already a function for it in my server I just have to send the notification to the user. Is it possible to achieve this using nodejs or is there a way to implement it in flutter?</p>
  <p>I found this code</p>
  <pre><code>    var FCM = require('fcm-node')
      var serverKey = require('path/to/privatekey.json') //put the generated private key path here            
      var fcm = new FCM(serverKey)     
      var message = { //this may vary according to the message type (single recipient, multicast, topic, et cetera)        
        to: 'registration_token',         
        collapse_key: 'your_collapse_key',                
        notification: {            
          title: 'Title of your push notification',             
          body: 'Body of your push notification'         
        },                
        data: {  //you can send only notification or only data(or include both)            
          my_key: 'my value',            
          my_another_key: 'my another value'        
        }    
      }        
      fcm.send(message, function(err, response){        
        if (err) {            
          console.log(&quot;Something has gone wrong!&quot;)        
        } else {            
          console.log(&quot;Successfully sent with response: &quot;, response)        
  </code></pre>
  <p>this is a npm package taht lets send a notification but it asks for a registration token.</p>
  <p>I hope you can help me. Thanks in advance!</p>