go 互斥锁

• sync.Mutex

sync.Mutex

• 互斥：保证每次只有一个 goroutine 可以访问一个共享的变量

• go 标准库提供 sync.Mutex 互斥锁类型及两个方法： Lock 和 Unlock

  • 在代码前调用 Lock，在代码后调用 Unlock 保证这段代码的互斥执行

  • 可用 defer 语句保证互斥锁一定会被解锁

    package main
    
    import (
    "fmt"
    "sync"
    "time"
    )
    
    // SafeCounter is safe to use concurrently.
    type SafeCounter struct {
    v   map[string]int
    mux sync.Mutex
    }
    
    // Inc increments the counter for the given key.
    func (c *SafeCounter) Inc(key string) {
    c.mux.Lock()
    // Lock so only one goroutine at a time can access the map c.v.
    c.v[key]++
    c.mux.Unlock()
    }
    
    // Value returns the current value of the counter for the given key.
    func (c *SafeCounter) Value(key string) int {
    c.mux.Lock()
    // Lock so only one goroutine at a time can access the map c.v.
    defer c.mux.Unlock()
    return c.v[key]
    }
    
    func main() {
    c := SafeCounter{v: make(map[string]int)}
    for i := 0; i < 1000; i++ {
    go c.Inc("somekey")
    }
    
    time.Sleep(time.Second)
    fmt.Println(c.Value("somekey"))
    }