golang获取本周、上周 周一日期

time.Weekday类型可以做运算，强制转int,会得到偏差数。
默认是 Sunday 开始到 Saturday 算 0,1,2,3,4,5,6

所以只有Monday减去Sunday的时候是正数，特殊处理下就可以了。

/**
获取本周周一的日期
*/
func GetFirstDateOfWeek() (weekMonday string) {
	now := time.Now()

	offset := int(time.Monday - now.Weekday())
	if offset > 0 {
		offset = -6
	}

	weekStartDate := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, time.Local).AddDate(0, 0, offset)
	weekMonday = weekStartDate.Format("2006-01-02")
	return
}

/**
获取上周的周一日期
*/
func GetLastWeekFirstDate() (weekMonday string) {
	thisWeekMonday := GetFirstDateOfWeek()
	TimeMonday, _ := time.Parse("2006-01-02", thisWeekMonday)
	lastWeekMonday := TimeMonday.AddDate(0, 0, -7)
	weekMonday = lastWeekMonday.Format("2006-01-02")
	return
}