how to get extra data from openLayers feature

Question

I have some GeoJSON files for my APP, I used these files as my Vector Layers source , I put some extra data in files like name, Enabled and..., I use to reading this file each time I need some more info but the thing is I want to achieve this info using layer.getSource().getFeatures()[0].get('name') but It wont work, how I can solve this problem thanks

{
"type": "FeatureCollection",
"crs": { "type": "name", "properties": { "name": "EPSG:3857" } },
"features": [
  {
    "type": "Feature",
    "geometry": {
     "type": "Point",
     "coordinates": [1742479.7678, 3201115.597099997]
   },
   "Enabled": 1,
   "volt": 0,
   "id": 1,

  }]} 

I want to get this info by layer.getSource().getFeatures()[0].get('volt')