github.com/graybobo/golang.org-package-offline-cache@v0.0.0-20200626051047-6608995c132f/x/talks/2012/10things/9.go (about)

     1  // +build OMIT
     2  
     3  package main
     4  
     5  import (
     6  	"fmt"
     7  	"time"
     8  	"math/rand"
     9  )
    10  
    11  func waiter(i int, block, done chan struct{}) {
    12  	time.Sleep(time.Duration(rand.Intn(3000)) * time.Millisecond)
    13  	fmt.Println(i, "waiting...")
    14  	<-block // HL
    15  	fmt.Println(i, "done!")
    16  	done <- struct{}{}
    17  }
    18  
    19  func main() {
    20  	block, done := make(chan struct{}), make(chan struct{})
    21  	for i := 0; i < 4; i++ {
    22  		go waiter(i, block, done)
    23  	}
    24  	time.Sleep(5 * time.Second)
    25  	close(block) // HL
    26  	for i := 0; i < 4; i++ {
    27  		<-done
    28  	}
    29  }
    30  // endmain OMIT