Uma function do google cloud que conecta com o firebase

index.js

var functions = require('firebase-functions');
var admin = require('firebase-admin');
var code = 404;
var result = "{\"message\": \"not found\"}";
var debug = '';

admin.initializeApp(
  {...},
  databaseURL: "https://amigosecreto-7d398.firebaseio.com/"
});

exports.amigos = functions.https.onRequest((req, res) => {
  var db = admin.database();
  var ref = db.ref("amigos");

  res.set('content-type','application/json');

  if (req.method == 'GET') {
    
    
    if (req.query.id != {}) {
      ref.once("value", function(snapshot) {

        var lista = snapshot.val();
        result = "{\"message\": \"" + req.query.id + " not found\"}";
      	if (typeof lista[req.query.id] !== 'undefined' && lista[req.query.id]) {
          code =  200;
      	  result = JSON.stringify(lista[req.query.id]);
     	}
      });

      res.status(code).end(result);
    }

    ref.once("value", function(snapshot) {
      	code = 200;
		result = JSON.stringify(snapshot);
    });

    res.status(code).end(result);
  }

  var message = "{\"message\": \"" + req.method + " not implemented\"}";

  res.status(405).end(message);
});

package.json

{
  "name": "amigos",
  "version": "0.0.1",
  "dependencies": {
    "firebase-functions": "0.6.3",
    "firebase-admin": "5.2.1"
  }
}