package main
import (
    "sync"
)
// 全局變量
var counter int
func main() {
    var wg sync.WaitGroup
    for i := 0; i < 1000; i++ {
        wg.Add(1)
        go func() {
            defer wg.Done()
            counter++
        }()
    }
    wg.Wait()
    println(counter)
}

// ... 省略之前部分
var wg sync.WaitGroup
var l sync.Mutex
for i := 0; i < 1000; i++ {
    wg.Add(1)
    go func() {
        defer wg.Done()
        l.Lock()
        counter++
        l.Unlock()
    }()
}
wg.Wait()
println(counter)
// ... 省略之后部分

package main
import (
    "sync"
)
// Lock try lock
type Lock struct {
    c chan struct{}
}
// NewLock generate a try lock
func NewLock() Lock {
    var l Lock
    l.c = make(chan struct{}, 1)
    l.c <- struct{}{}
    return l
}
// Lock try lock, return lock result
func (l Lock) Lock() bool {
    lockResult := false
    select {
    case <-l.c:
        lockResult = true
    default:
    }
    return lockResult
}
// Unlock , Unlock the try lock
func (l Lock) Unlock() {
    l.c <- struct{}{}
}
var counter int
func main() {
    var l = NewLock()
    var wg sync.WaitGroup
    for i := 0; i < 10; i++ {
        wg.Add(1)
        go func() {
            defer wg.Done()
            if !l.Lock() {
                // log error
                println("lock failed")
                return
            }
            counter++
            println("current counter", counter)
            l.Unlock()
        }()
    }
    wg.Wait()
}

package main
import (
    "fmt"
    "sync"
    "time"
    "github.com/go-redis/redis"
)
func incr() {
    client := redis.NewClient(&redis.Options{
        Addr:     "localhost:6379",
        Password: "", // no password set
        DB:       0,  // use default DB
    })
    var lockKey = "counter_lock"
    var counterKey = "counter"
    // lock
    resp := client.SetNX(lockKey, 1, time.Second*5)
    lockSuccess, err := resp.Result()
    if err != nil || !lockSuccess {
        fmt.Println(err, "lock result: ", lockSuccess)
        return
    }
    // counter ++
    getResp := client.Get(counterKey)
    cntValue, err := getResp.Int64()
    if err == nil {
        cntValue++
        resp := client.Set(counterKey, cntValue, 0)
        _, err := resp.Result()
        if err != nil {
            // log err
            println("set value error!")
        }
    }
    println("current counter is ", cntValue)
    delResp := client.Del(lockKey)
    unlockSuccess, err := delResp.Result()
    if err == nil && unlockSuccess > 0 {
        println("unlock success!")
    } else {
        println("unlock failed", err)
    }
}
func main() {
    var wg sync.WaitGroup
    for i := 0; i < 10; i++ {
        wg.Add(1)
        go func() {
            defer wg.Done()
            incr()
        }()
    }
    wg.Wait()
}

package main
import (
    "time"
    "github.com/samuel/go-zookeeper/zk"
)
func main() {
    c, _, err := zk.Connect([]string{"127.0.0.1"}, time.Second) //*10)
    if err != nil {
        panic(err)
    }
    l := zk.NewLock(c, "/lock", zk.WorldACL(zk.PermAll))
    err = l.Lock()
    if err != nil {
        panic(err)
    }
    println("lock succ, do your business logic")
    time.Sleep(time.Second * 10)
    // do some thing
    l.Unlock()
    println("unlock succ, finish business logic")
}

package main
import (
    "log"
    "github.com/zieckey/etcdsync"
)
func main() {
    m, err := etcdsync.New("/lock", 10, []string{"http://127.0.0.1:2379"})
    if m == nil || err != nil {
        log.Printf("etcdsync.New failed")
        return
    }
    err = m.Lock()
    if err != nil {
        log.Printf("etcdsync.Lock failed")
        return
    }
    log.Printf("etcdsync.Lock OK")
    log.Printf("Get the lock. Do something here.")
    err = m.Unlock()
    if err != nil {
        log.Printf("etcdsync.Unlock failed")
    } else {
        log.Printf("etcdsync.Unlock OK")
    }
}

package main
import (
    "fmt"
    "time"
    "github.com/garyburd/redigo/redis"
    "gopkg.in/redsync.v1"
)
func newPool(server string) *redis.Pool {
    return &redis.Pool{
        MaxIdle:     3,
        IdleTimeout: 240 * time.Second,
        Dial: func() (redis.Conn, error) {
            c, err := redis.Dial("tcp", server)
            if err != nil {
                return nil, err
            }
            return c, err
        },
        TestOnBorrow: func(c redis.Conn, t time.Time) error {
            _, err := c.Do("PING")
            return err
        },
    }
}
func newPools(servers []string) []redsync.Pool {
    pools := []redsync.Pool{}
    for _, server := range servers {
        pool := newPool(server)
        pools = append(pools, pool)
    }
    return pools
}
func main() {
    pools := newPools([]string{"127.0.0.1:6379", "127.0.0.1:6378", "127.0.0.1:6377"})
    rs := redsync.New(pools)
    m := rs.NewMutex("/lock")
    err := m.Lock()
    if err != nil {
        panic(err)
    }
    fmt.Println("lock success")
    unlockRes := m.Unlock()
    fmt.Println("unlock result: ", unlockRes)
}