curl -vsH "Content-Type: application/json" \
  -X GET 'https://firestore.googleapis.com/v1beta1/projects/projectIDhere/databases/(default)/documents/collectionName/documentID01?mask.fieldPaths=name2'


{
  "name": "projects/projectIDhere/databases/(default)/documents/collectionName/documentID01",
  "fields": {
    "name2": {
      "stringValue": "test2"
    }
  },
  "createTime": "2018-01-16T05:50:16.345709Z",
  "updateTime": "2018-01-16T05:50:16.345709Z"
}