Add duration function to templates

Signed-off-by: Vadim Aleksandrov <valeksandrov@me.com>

docs/notifications.md

@@ -97,3 +97,4 @@ templating.
 | stringSlice | ...string | Returns the passed strings as a slice of strings. |
 | date | string, time.Time | Returns the text representation of the time in the specified format. For documentation on formats refer to [pkg.go.dev/time](https://pkg.go.dev/time#pkg-constants). |
 | tz | string, time.Time | Returns the time in the timezone. For example, Europe/Paris. |
+| duration | string | Returns the time.Duration representation of a passed string. |

template/template.go

@@ -204,6 +204,10 @@ var DefaultFuncs = FuncMap{
 		}
 		return t.In(loc), nil
 	},
+	// duration returns the time.Duration representation of a passed string
+	"duration": func(text string) (time.Duration, error) {
+		return time.ParseDuration(text)
+	},
 }
 
 // Pair is a key/value string pair.

template/template_test.go

@@ -522,6 +522,14 @@ func TestTemplateFuncs(t *testing.T) {
 		in:     `{{ . | tz "Invalid/Timezone" }}`,
 		data:   time.Date(2024, 1, 1, 8, 15, 30, 0, time.UTC),
 		expErr: "template: :1:7: executing \"\" at <tz \"Invalid/Timezone\">: error calling tz: unknown time zone Invalid/Timezone",
+	}, {
+		title: "Template using duration",
+		in:    `{{ "60s" | duration | printf "%d" }}`,
+		exp:   "60000000000",
+	}, {
+		title:  "Template using invalid duration",
+		in:     `{{ "60k" | duration | printf "%d" }}`,
+		expErr: "template: :1:11: executing \"\" at <duration>: error calling duration: time: unknown unit \"k\" in duration \"60k\"",
 	}} {
 		tc := tc
 		t.Run(tc.title, func(t *testing.T) {