go_cond_usage.go

package main

import (
	"fmt"
	"sync"
	"time"
	"runtime"
)

func main() {
	m := sync.Mutex{}
	c := sync.NewCond(&m)
	go func() {
		c.L.Lock()
		fmt.Println("started go routine1 - ", runtime.NumGoroutine())
		for !cond() {
			fmt.Println("started wait1 - ", runtime.NumGoroutine())
			c.Wait()
			fmt.Println("ended wait1 - ", runtime.NumGoroutine())
		} 
		fmt.Println("end go routine1 - ", runtime.NumGoroutine())
		c.L.Unlock()
	}()
	go func() {
		fmt.Println("started go routine2 - ", runtime.NumGoroutine())
		c.L.Lock()
		for !cond() {
			fmt.Println("started wait2 - ", runtime.NumGoroutine())
			c.Wait()
			fmt.Println("ended wait2 - ", runtime.NumGoroutine())
		}
		c.L.Unlock()
		fmt.Println("end go routine2 - ", runtime.NumGoroutine())
	}()
	
	time.Sleep(time.Second * 2)
	fmt.Println("Hello, playground - ", runtime.NumGoroutine())
	c.L.Lock()
	c.Broadcast()
	c.L.Unlock()
	time.Sleep(time.Second * 2)
	fmt.Println("Hello, playground2 - ", runtime.NumGoroutine())
	time.Sleep(time.Second * 15)
	fmt.Println("Hello, playground3 - ", runtime.NumGoroutine())
}

func cond() bool {
//	time.Sleep(10 * time.Second)
	return true
}