code_reading/basic/goroutine/wg.go at master · mannadt/code_reading · GitHub

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package main

import (
	"fmt"
	"sync"
)

func wg() {
	var wg sync.WaitGroup
	for i := 0; i < 10; i++ {
		wg.Add(1)
		go func(i int) {
			if i < 5 {
				fmt.Println(i)
			}
			defer wg.Done()
		}(i)
	}
	wg.Wait()
	fmt.Println("finished")
}

// Tip: waitGroup 不要进行copy
func errWg1() {
	var wg sync.WaitGroup
	for i := 0; i < 10; i++ {
		wg.Add(1)
		go func(i int, wg sync.WaitGroup) {
			fmt.Println(i)
			defer wg.Done()
		}(i, wg)
	}
	wg.Wait()
	fmt.Println("finished")
}

// Tip: waitGroup 的 Add 要在goroutine前执行
func errWg2() {
	var wg sync.WaitGroup
	for i := 0; i < 10; i++ {
		go func(i int) {
			wg.Add(1)
			fmt.Println(i)
			defer wg.Done()
		}(i)
	}
	wg.Wait()
	fmt.Println("finished")
}

// Tip: waitGroup 的 Add 很大会有影响吗？
func errWg3() {
	var wg sync.WaitGroup
	for i := 0; i < 10; i++ {
		wg.Add(100)
		go func(i int) {
			fmt.Println(i)
			defer wg.Done()
			wg.Add(-100)
		}(i)
	}
	fmt.Println("finished")
}