Stream connector | Elastic events how to get hostgroup

Hello everyone,

I want to add hostgroup name for neb service and host status on my elastic events format using by my stream connector.

I've tried several ways but nothing works yet.

Do you have an idea for getting a group of hosts?

my current working file : 

# cat elastic-events-format.json
{
  "neb_host_status": {
    "event_type": "host",
    "state": "{state}",
    "state_type": "{state_type}",
    "hostname": "{cache.host.name}",
    "output": "{output}",
    "notes": "{cache.host.notes}",
    "timestamp": "{last_check}"
  },
  "neb_service_status": {
    "event_type": "service",
    "state": "{state}",
    "state_type": "{state_type}",
    "hostname": "{cache.host.name}",
    "output": "{output}",
    "notes": "{cache.service.notes}",
    "service" : "{cache.service.description}",
    "hostgroup_name": "{cache.host.group_name}",
    "timestamp": "{last_check}"
  }
}