Slack-Alerting | JSON Body

Hello All,

I am testing Kibana to Slack feature. Where, I am receiving a alert message on Slack but no data is present in there.

  "actions": {
    "incoming-webhook": {
      "throttle_period_in_millis": 10000,
      "webhook": {
        "scheme": "https",
        "host": "hooks.slack.com",
        "port": 443,
        "method": "post",
        "path": "/services/<keys>",
        "params": {},
        "headers": {},
        "body": "{\"text\":\"{{#ctx.payload.hits.hits}} \n Instance: {{_source.event.instance}} \n Type: {{_source.event.type}} \n Name: {{_source.event.name}} \n Link: {{_source.event.link}} \n Threat: {{_source.event.threatName}} \n Hostname: {{_source.event.hostname}} \n avScore: {{_source.event.avPositives}}/{{_source.event.avTotal}} \n  Synapse: {{_source.event.synapse}} \n   Flag: {{_source.event.flagName}} \n    \n {{/ctx.payload.hits.hits}}    \"}"

Need some inputs.