package

1_1_User.go

package usertype User struct {Name string
}

1_1_UserGet.go

package userfunc GetCourse(c User) string {return c.Name
}

1_1_UserMain.go

package mainimport ("fmt"Userch03 "goproj/IMOOC/ch03/user"//别名，防止同名歧义
)func main() {c := Userch03.User{Name: "hi,user",}fmt.Println(Userch03.GetCourse(c))
}

gin

github链接

package mainimport ("net/http""github.com/gin-gonic/gin"
)func main() {r := gin.Default()r.GET("/ping", func(c *gin.Context) {c.JSON(http.StatusOK, gin.H{"message": "pong",})})r.Run() // listen and serve on 0.0.0.0:8080 (for windows "localhost:8080")
}

首次使用时，包的导入报错：
鼠标放在"github.com/gin-gonic/gin"，出现提示框，点击Sycn…，等一会报错消失
Sync过程自动下载，可以在go.mod中看到

或者在终端打开、go mod tidy

单元测试

package mainfunc add(a, b int) int {return a + b
}

package mainimport "testing"func TestAdd(t *testing.T) {if testing.Short(){t.Skip("short模式")}re := add(1, 2)if re != 3 {t.Errorf("expect:%d,actual:%d", 3, re)}
}

终端go test

测试函数前的运行箭头右键后

基于表格

func TestAdd2(t *testing.T) {var dataset = []struct {a   intb   intout int}{{1, 1, 2},{-9, 8, 1},{0, 0, 0},}for _, value := range dataset {re := add(value.a, value.b)if re != value.out {t.Errorf("expect:%d,actual:%d", 3, re)}}
}

性能测试

const numbers = 10000func BenchmarkStringSprintf(b *testing.B) {b.ResetTimer()for i := 0; i < b.N; i++ {var str stringfor j := 0; j < numbers; j++ {str = fmt.Sprintf("%s%d", str, j)}}b.StopTimer()
}func BenchmarkStringAdd(b *testing.B) {b.ResetTimer()for i := 0; i < b.N; i++ {var str stringfor j := 0; j < numbers; j++ {str += strconv.Itoa(j)}}b.StopTimer()
}func BenchmarkStringBuilder(b *testing.B) {b.ResetTimer()for i := 0; i < b.N; i++ {var builder strings.Builderfor j := 0; j < numbers; j++ {builder.WriteString(strconv.Itoa(j))}_ = builder.String()}b.StopTimer()
}

并发编程

package mainimport ("fmt""time"
)func asyncPrint() {time.Sleep(time.Second)fmt.Println("hi")
}func main() {go asyncPrint()fmt.Println("main")time.Sleep(2 * time.Second)fmt.Println("main2")
}

import "fmt"func main() {fmt.Println("method1")for i := 0; i < 100; i++ {go func() {fmt.Println(i)}()}//fmt.Println("method2")//for i := 0; i < 100; i++ {//	tmp := i//	go func() {//		fmt.Println(tmp)//	}()//}//fmt.Println("method3")//for i := 0; i < 100; i++ {//	go func(i int) {//		fmt.Println(i)//	}(i)//}
}

waitgroup

package mainimport ("fmt""sync"
)func main() {var wg sync.WaitGroupwg.Add(100)fmt.Println("method3")for i := 0; i < 100; i++ {go func(i int) {defer wg.Done()fmt.Println(i)}(i)}wg.Wait()
}

互斥锁mutex

package mainimport ("fmt""sync""sync/atomic"
)var total int32
var wg sync.WaitGroup
var lock sync.Mutexfunc add() {defer wg.Done()for i := 0; i < 10000; i++ {atomic.AddInt32(&total, 1)//lock.Lock()//total += 1//lock.Unlock()}
}func sub() {defer wg.Done()for i := 0; i < 10000; i++ {atomic.AddInt32(&total, -1)//lock.Lock()//total -= 1//lock.Unlock()}
}func main() {wg.Add(2)go add()go sub()wg.Wait()fmt.Println(total)fmt.Println("all done")
}

读写锁rwlock

package mainimport ("fmt""sync""time"
)func main() {var rwlock sync.RWMutexvar wg sync.WaitGroupwg.Add(6)//写锁go func() {time.Sleep(3 * time.Second)rwlock.Lock()defer rwlock.Unlock()fmt.Println("writing")time.Sleep(5 * time.Second)fmt.Println("write finish")}()time.Sleep(time.Second)//读锁for i := 0; i < 5; i++ {go func() {defer wg.Done()for j := 0; j < 10; j++ {rwlock.RLock()time.Sleep(500 * time.Millisecond)fmt.Println("read")rwlock.RUnlock()}}()}wg.Wait()
}

channel

package mainimport "fmt"func main() {//有缓存var msg1 chan stringmsg1 = make(chan string, 1) //1是缓存空间大小msg1 <- "harry"data := <-msg1fmt.Println(data)//无缓存,happen-before机制var msg2 chan stringmsg2 = make(chan string, 0)go func(msg2 chan string) {data2 := <-msg2fmt.Println(data2)}(msg2)msg2 <- "potter"var msg3 chan intmsg3 = make(chan int, 2)go func(msg3 chan int) {for data3 := range msg3 {fmt.Println(data3)}fmt.Println("all done")}(msg3)msg3 <- 1msg3 <- 2close(msg3)var ch1 chan int   //双向var ch2 chan<- int //只写入var ch3 <-chan int //只读取c := make(chan int, 3)var send chan<- int = cvar receive <-chan int = c
}

打印数字和字母

package mainimport ("fmt""time"
)var number, letter = make(chan bool), make(chan bool)func printNum() {i := 1for {<-numberfmt.Printf("%d%d", i, i+1)i += 2letter <- true}`在这里插入代码片`
}func printLetter() {i := 0str := "ABCDEFGHIJKLMNOPQRSTUVWXYZ"for {<-letterif i >= len(str) {return}fmt.Print(str[i : i+2])i += 2number <- true}
}func main() {go printNum()go printLetter()number <- truetime.Sleep(100 * time.Second)
}

select

package mainimport ("fmt""time"
)// 空结构体不占内存、channel多线程安全
var done = make(chan struct{})func g1(ch1 chan struct{}) {time.Sleep(time.Second)ch1 <- struct{}{}
}func g2(ch2 chan struct{}) {time.Sleep(1 * time.Second)ch2 <- struct{}{}
}func main() {ch1 := make(chan struct{})ch2 := make(chan struct{})go g1(ch1)go g2(ch2)//执行先就绪的channel，都就绪则随机（防止饥饿）//select {//case <-ch1://	fmt.Println("g1 done")//case <-ch2://	fmt.Println("g2 done")//default://	fmt.Println("default")//}timer := time.NewTimer(5 * time.Second)select {case <-ch1:fmt.Println("g1 done")case <-ch2:fmt.Println("g2 done")case <-timer.C:fmt.Println("time our")return}
}

context

package mainimport ("fmt""sync""time"
)var wgc sync.WaitGroupfunc cpuInfo(stop chan struct{}) {defer wgc.Done()for {select {case <-stop:fmt.Println("退出CPU监控")returndefault:time.Sleep(2 * time.Second)fmt.Println("CPU信息")}}
}func main() {var stop = make(chan struct{})wgc.Add(1)go cpuInfo(stop)time.Sleep(6 * time.Second)stop <- struct{}{}wgc.Wait()fmt.Println("监控完成")
}

package mainimport ("context""fmt""sync""time"
)var wgc2 sync.WaitGroupfunc cpuInfo2(ctx context.Context) {defer wgc2.Done()for {select {case <-ctx.Done():fmt.Println("退出CPU监控")returndefault:time.Sleep(2 * time.Second)fmt.Println("CPU信息")}}
}func main() {wgc2.Add(1)ctx, cancel := context.WithCancel(context.Background())go cpuInfo2(ctx)time.Sleep(6 * time.Second)cancel()wgc2.Wait()fmt.Println("监控完成")
}