package main

import (
	"context"
	"fmt"
	"testing"
	"time"
)

type A struct {
}

func B() *A {
	return nil
}

func Test1(t *testing.T) {
	var a interface{}
	a = B()
	fmt.Println(a == nil) // false
}

func Test2(t *testing.T) {
	c1 := context.Background()
	c2, cancel2 := context.WithCancel(c1)
	c3, _ := context.WithCancel(c2)

	go func() {
		select {
		case <-c3.Done():
			fmt.Println("c3 cancel")
		}
	}()

	time.Sleep(time.Second * 5)
	cancel2()
	fmt.Println("cancel2")

	//time.Sleep(time.Second * 5)
	//cancel3()
	//fmt.Println("cancel3")

	time.Sleep(time.Minute)
}

func Test3(t *testing.T) {
	n := time.Now()
	y, m, d := n.Date()
	n = time.Date(y, m, d, 0, 0, 0, 0, time.Local)
	st := n.AddDate(0, 0, -int(n.Weekday()))
	et := n.AddDate(0, 0, 7-int(n.Weekday()))
	fmt.Println(st, et)
}