golang中使用switch语句根据年月计算天数

package main

import "fmt"

func main() {
	days := CalcDaysFromYearMonth(2021, 9)
	fmt.Println(days)
}
func CalcDaysFromYearMonth(year, month int) (days int8) {
   /* 根据年月计算天数 */
   switch month {
   case 1, 3, 5, 7, 8, 10, 12:
      days = 31
   case 4, 6, 9, 11:
      days = 30
   case 2:
      if year%4 == 0 {
         days = 29 // 闰年
      } else {
         days = 28 // 平年
      }
   default:
      days = -1
   }
   return days
}