close-channel.go

// https://play.golang.org/p/jUzWcBiO4xJ
// Output:
// B 0
// A 0
// end

package main

import (
	"fmt"
	"time"
)

func funcA(a chan int) {
	go funcB(a)
	select {
	case i := <- a:
		fmt.Println("A", i)
	}
}

func funcB(a chan int) {
	select {
	case i := <- a:
		fmt.Println("B", i)
	}
}

func main() {
	a := make(chan int)
	go funcA(a)
	time.Sleep(3 * time.Second)
	close(a)
	time.Sleep(1 * time.Second)
	fmt.Println("end")
}

sample-channel.go

// https://play.golang.org/p/HCVfN1tkLQO
// Output:
// A 3
// end
package main

import (
	"fmt"
	"time"
)

func funcA(a chan int) {
	go funcB(a)
	select {
	case i := <- a:
		fmt.Println("A", i)
	}
}

func funcB(a chan int) {
	select {
	case i := <- a:
		fmt.Println("B", i)
	}
}

func main() {
	a := make(chan int)
	go funcA(a)
	time.Sleep(3 * time.Second)
	a <- 3
	time.Sleep(1 * time.Second)
	fmt.Println("end")
}

sample-context.go

// https://play.golang.org/p/DsHHxVMMGM1
// Output:
// B canceled
// A canceled
// end
package main

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

func funcA(ctx context.Context) {
	go funcB(ctx)
	select {
	case <- ctx.Done():
		fmt.Println("A canceled")
	}
}

func funcB(ctx context.Context) {
	select {
	case <- ctx.Done():
		fmt.Println("B canceled")
	}
}

func main() {
	ctx, cancel := context.WithCancel(context.Background())
	go funcA(ctx)
	time.Sleep(3 * time.Second)
	cancel()
	time.Sleep(1 * time.Second)
	fmt.Println("end")
}