1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15

func RunWithTimeout(fun func() error, timeout time.Duration) error {
	finished := make(chan struct{})
	var err error
	go func() {
		err = fun()
		finished <- struct{}{}
	}()

	select {
	case <-finished:
		return err
	case <-time.After(timeout):
		return fmt.Errorf("timeout")
	}
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12

// 删除 user 时，也删除 user 的 account
db.Select("Account").Delete(&user)

// 删除 user 时，也删除 user 的 Orders、CreditCards 记录
db.Select("Orders", "CreditCards").Delete(&user)

// 删除 user 时，也删除用户所有 has one/many、many2many 记录
db.Select(clause.Associations).Delete(&user)

// 删除 users 时，也删除每一个 user 的 account
db.Select("Account").Delete(&users)

1
2
3
4
5

type Human struct {
	Name string
} 

var people = Human{Name:"zhangsan"}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49

package main

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

func main() {
	var state = make(map[int]int)
	var mutex = &sync.Mutex{}
	var ops int64 = 0
	for r := 0; r < 100; r++ {
		// 运行100个go协程来重复读取state
		go func() {
			total := 0
			for {
				key := rand.Intn(5)
				mutex.Lock()
				total += state[key]
				mutex.Unlock()
				atomic.AddInt64(&ops, 1)
				runtime.Gosched() // 为了确保这个Go协程不会在调度中饿死，我们在每次操作后明确的使用runtime.Gosched()进行释放。是自动处理的。
			}
		}()
	}
	for w := 0; w < 10; w++ { // 模拟写入操作
		go func() {
			for {
				key := rand.Intn(5)
				val := rand.Intn(100)
				mutex.Lock()
				state[key] = val
				mutex.Unlock()
				atomic.AddInt64(&ops, 1)
				runtime.Gosched()
			}
		}()
	}
	time.Sleep(time.Second)
	opsFinal := atomic.LoadInt64(&ops)
	fmt.Println("ops:", opsFinal)
	mutex.Lock() //对 state 使用一个最终的锁，显示它是如何结束的。
	fmt.Println("state:", state)
	mutex.Unlock()
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16

func doSomething() {
    m.Lock()
    item := ...
    http.Get()  // 各种耗时的 IO 操作
    m.Unlock()
}

// 改为
func doSomething() {
    m.Lock()
    item := ...
    m.Unlock()

    http.Get()
}

1
2
3
4
5
6
7

	var mail = make(chan string)
    go func() {
        <- mail
        fmt.Println("get chance to do something")
    }()
    time.Sleep(5*time.Second)
    mail <- "moximoxi"