How to get value of "for" duration from alerting rule?

[Zahar Celac]

Hello!

Let's take alert example from from official doc:

# Alert for any instance that is unreachable for >5 minutes.
  - alert: InstanceDown
    expr: up == 0
    for: 5m
    labels:
      severity: page
    annotations:
      summary: "Instance {{ $labels.instance }} down"
      description: "{{ $labels.instance }} of job {{ $labels.job }} has been down for more than 5 minutes."

Is it possible to get value from "for" clause (in this case ti will be "5m") so we can use it further in annotation section?

For exaple let's call it {{ $for_duraton }} :

description: "{{ $labels.instance }} of job {{ $labels.job }} has been down for more than {{ $for_duration }}."