Go from introduction to practice -- shared memory concurrency mechanism (notes)

Shared memory concurrency mechanism

Lock

Error model

package share_test

import (
	"testing"
	"time"
)

func TestCounter(t *testing.T) {
    
	coun := 0
	for i := 0; i < 5000; i++ {
    
		go func() {
    
			coun++
		}()
	}
	time.Sleep(time.Second)
	t.Log(coun)
}

Self augmentation in different processes , Increased competition . Not a thread safe program

Write it correctly

func TestCounterThreadSafe(t *testing.T) {
    
	var mut sync.Mutex
	coun := 0
	for i := 0; i < 5000; i++ {
    
		go func() {
    
			defer func() {
    
				mut.Unlock()
			}()
			mut.Lock()
			coun++
		}()
	}
	time.Sleep(time.Second)
	t.Log(coun)
}

WaitGroup

func TestCounterWaitGroup(t *testing.T) {
    
	var wg sync.WaitGroup
	var mut sync.Mutex
	coun := 0
	for i := 0; i < 5000; i++ {
    
		wg.Add(1)
		go func() {
    
			mut.Lock()
			defer func() {
    
				mut.Unlock()
			}()
			coun++
			wg.Done()
		}()
	}
	wg.Wait()
	t.Log(coun)
}

Precisely control the waiting time