Add the sprig functions in the template engine

vendor/github.com/Masterminds/sprig/date.go

@@ -0,0 +1,53 @@
+package sprig
+
+import (
+	"time"
+)
+
+// Given a format and a date, format the date string.
+//
+// Date can be a `time.Time` or an `int, int32, int64`.
+// In the later case, it is treated as seconds since UNIX
+// epoch.
+func date(fmt string, date interface{}) string {
+	return dateInZone(fmt, date, "Local")
+}
+
+func htmlDate(date interface{}) string {
+	return dateInZone("2006-01-02", date, "Local")
+}
+
+func htmlDateInZone(date interface{}, zone string) string {
+	return dateInZone("2006-01-02", date, zone)
+}
+
+func dateInZone(fmt string, date interface{}, zone string) string {
+	var t time.Time
+	switch date := date.(type) {
+	default:
+		t = time.Now()
+	case time.Time:
+		t = date
+	case int64:
+		t = time.Unix(date, 0)
+	case int:
+		t = time.Unix(int64(date), 0)
+	case int32:
+		t = time.Unix(int64(date), 0)
+	}
+
+	loc, err := time.LoadLocation(zone)
+	if err != nil {
+		loc, _ = time.LoadLocation("UTC")
+	}
+
+	return t.In(loc).Format(fmt)
+}
+
+func dateModify(fmt string, date time.Time) time.Time {
+	d, err := time.ParseDuration(fmt)
+	if err != nil {
+		return date
+	}
+	return date.Add(d)
+}