1. 只运行一次

package once_test
import (
    "fmt"
    "sync"
    "testing"
    "unsafe"
)
type Singleton struct {
}
var singleInstance *Singleton
var once sync.Once
func GetSingletonObj() *Singleton {
    once.Do(func() {
        fmt.Println("Create obj")
        singleInstance = new(Singleton)
    })
    return singleInstance
}
func TestGetSingletonObj(t *testing.T) {
    var wg sync.WaitGroup
    for i := 0; i < 10; i++ {
        wg.Add(1)
        go func() {
            obj := GetSingletonObj()
            fmt.Printf("%x\n", unsafe.Pointer(obj))
            wg.Done()
        }()
    }
    wg.Wait()
}

2. 仅需任意任务完成

package concurrency
import (
    "fmt"
    "runtime"
    "testing"
    "time"
)
func runTask(id int) string {
    time.Sleep(10 * time.Millisecond)
    return fmt.Sprintf("The result is from %d", id)
}
func FirstResponse() string {
    numOfRunner := 10
    //采用buffer channel 来防止协程泄露
    ch := make(chan string, numOfRunner)
    //ch := make(chan string)
    for i := 0; i < numOfRunner; i++ {
        go func(i int) {
            ret := runTask(i)
            ch <- ret
        }(i)
    }
    return <-ch
}
func TestFirstResponse(t *testing.T) {
    t.Log("Before:", runtime.NumGoroutine())
    t.Log(FirstResponse())
    time.Sleep(time.Second * 1)
    t.Log("After:", runtime.NumGoroutine())
}

3. 所有任务完成

package util_all_done
import (
    "fmt"
    "runtime"
    "testing"
    "time"
)
func runTask(id int) string {
    time.Sleep(10 * time.Millisecond)
    return fmt.Sprintf("The result is from %d", id)
}
func FirstResponse() string {
    numOfRunner := 10
    ch := make(chan string, numOfRunner)
    for i := 0; i < numOfRunner; i++ {
        go func(i int) {
            ret := runTask(i)
            ch <- ret
        }(i)
    }
    return <-ch
}
func AllResponse() string {
    numOfRunner := 10
    ch := make(chan string, numOfRunner)
    for i := 0; i < numOfRunner; i++ {
        go func(i int) {
            ret := runTask(i)
            ch <- ret
        }(i)
    }
    finalRet := ""
    for j := 0; j < numOfRunner; j++ {
        finalRet += <-ch + "\n"
    }
    return finalRet
}
func TestFirstResponse(t *testing.T) {
    t.Log("Before:", runtime.NumGoroutine())
    t.Log(AllResponse())
    time.Sleep(time.Second * 1)
    t.Log("After:", runtime.NumGoroutine())
}

4. 对象池

5. sync.pool对象缓存