LockMap

Motivation

This is a recurrent pattern I met in different situations. For example:

• When we need to process an HTTP request if the result is cacheable: we want to wait one request to finish and then to copy the result to everybody who requested it.
• When we need to allow only one goroutine to send a request out (which depends on variables).
• etc.

Quick start

Synchronous locking:

lm := lockmap.New()

...

    ctx := context.Background()

    unlocker := lm.Lock(ctx, "key1")
    defer unlocker.Unlock()

    // do something with key1

Asynchronous locking:

lm := lockmap.New()

...

    ctx, cancelFn := context.WithTimeout(context.Background(), time.Second*30)
    defer cancelFn()

    unlocker, waiter := lm.LockAsync(ctx, "key1")
    defer func(){
        <-waiter.C
        if unlocker.IsLocked() {
            unlocker.Unlock()
        }
    }()

    select {
    case <-waiter.C:
        if !unlocker.IsLocked() {
            // reached 30sec timeout
            return
        }
        // do something with key1
    case <-someOtherChan:
        cancelFn()
        // do something else
    }