How to perform time functions in go template?

[Deepika]

Objective: To subtract 10 minutes from go's time.Time object(".StartsAt") in html template (In specific the prometheus alertmanager's email template: email_template.tmpl)

Code: <tr><td>error_timestamp</td><td>{{ .StartsAt }}</td></tr>

Alertmanager version: 0.20.0

Options tried and corresponding errors :

1. <td>{{ .StartsAt.Add(-10*time.Minute) }}</td>  ::::::: Unexpected operand "("

2. <td>{{ .StartsAt.Add "-10*time.Minute" }}</td>  :::::::  expected integer; found "-10*time.Minute\""

3.  {{ $timestamp := .StartsAt.Add "10m" }} :::::::::::::::: wrong type for value; expected time.Duration; got string

4.  {{ $timestamp :=  Add .StartsAt "10m" }} ::::::::::: Add function not defined

5.  {{ $timestamp :=  .StartsAt.Add -10*time.Minute }} :::::::::::: time function not defined

6.  {{ $timestamp :=  .StartsAt.Add (-10*time.Minute) }} :::::::::::: illegal operand *

7.  {{ $timestamp :=  .StartsAt.Add (time.duration "10m") }} :::::::::::: duration function not defined 

8. {{ $timestamp :=  .StartsAt.Add (time.ParseDuration "10m") }} ::::::::::::  time function not defined

9.  {{ $timestamp :=  .StartsAt.Add 10 }} ::::::::::: No error. But no change in timestamp too.

[Tamás Gulácsi]

Either add a TimeAdd function to the template's FuncMap, or use a constant:

 

    {{ $timestamp := .StartsAt.Add 60000000000 }} //10m is 60000000000 ns