now.go
func (now *Now) BeginningOfWeek() time.Time {
	t := now.BeginningOfDay()
	weekday := int(t.Weekday())

	if WeekStartDay != time.Sunday {
		weekStartDayInt := int(WeekStartDay)

		if weekday < weekStartDayInt {
			weekday = weekday + 7 - weekStartDayInt
		} else {
			weekday = weekday - weekStartDayInt
		}
	}
	return t.AddDate(0, 0, -weekday)
}
func (now *Now) BeginningOfWeek() time.Time {
	t := now.BeginningOfDay()
	weekday := int(t.Weekday())

	if WeekStartDay != time.Sunday {
		weekStartDayInt := int(WeekStartDay)

		if weekday < weekStartDayInt {
			weekday = weekday + 7 - weekStartDayInt
		} else {
			weekday = weekday - weekStartDayInt
		}
	}
	return t.AddDate(0, 0, -weekday)
}
// BeginningOfWeek beginning of week