确保只有一个goroutine正在使用sync.Map运行

Question

I have a HTTP handler which receives a parameter from query. I don't want to run this handler concurrently for the same query parameter i.e. only one goroutine should be running at a point in time.

This was my idea:

import "sync"
import "fmt"

var safeMap = sync.Map{}

func handler(c) {

    _, loaded := safeMap.LoadOrStore(c.param, 1) // loaded is true if value was loaded and false if stored 
    fmt.Println(loaded)

    if loaded {
        c.JSON(http.StatusLocked, "locked")
        return
    }

    go doWork(c.param)

    safeMap.Delete(c.param)

    c.JSON(http.StatusOK, "done")
}

But, whenever I send two concurrent requests loaded is false for both and both requests are processed. Why?

Answer 1

You're starting a goroutine to do the work, then immediately deleting the key, before the work has a chance to complete. So the chance of lock contention is infinitesimally low.

Why are you using go doWork() instead of just doWork()?