_script is not getting referred

[Binu_Andrews]

I am trying to access below script from an email action. The action is getting triggered, but the email subject is not getting fetched from the template. insted of that, what ever i mentioned as the id name is going as the email subject.

_script
{
"_id" : "email_subject",
"found" : true,
"script" : {
"lang" : "mustache",
"source" : "test email subject"
}
}

Email Action

"email" : {
      "profile" : "standard",
      "to" : [
        "abc@xxx.com"
      ],
      "subject" : {
        "id":"email_subject"
      },
      "body" : {
        "text" : "Watch [{{ctx.metadata.name}}] has exceeded the threshold"
      }
    }