chan_signaling_patterns.go

package main

import (
	"fmt"
	"math/rand"
	"sync"
	"time"
)

func main() {

	var wg sync.WaitGroup
	wg.Add(2)
	//waitForTaskPattern(&wg)
	//waitForResultPattern(&wg)
	waitForFinishPattern(&wg)
	wg.Wait()
}

func waitForTaskPattern(wg *sync.WaitGroup) {

	c := make(chan string) //unbuffered channel

	go func() {
		fmt.Println("start blocking the employee goroutine")
		value := <-c
		fmt.Println("received value:", value)
		wg.Done()
	}()

	sd := time.Duration(rand.Intn(500)) * time.Millisecond
	time.Sleep(sd)

	c <- "hello"
	fmt.Println("sending data")
	wg.Done()
}

func waitForResultPattern(wg *sync.WaitGroup) {

	c := make(chan string)

	go func() {
		time.Sleep(200 * time.Millisecond)
		c <- "hello"
		fmt.Println("sending value")
		wg.Done()
	}()

	value := <-c
	fmt.Println("received value:", value)
	wg.Done()
}

func waitForFinishPattern(wg *sync.WaitGroup) {

	c := make(chan struct{})

	go func() {
		time.Sleep(200 * time.Millisecond)
		close(c)
		fmt.Println("sending close signal")
		wg.Done()
	}()

	_, wd := <-c

	fmt.Println("receive data?", wd)
	wg.Done()
}