How can I generalize this map access/modification pattern, considering there aren't generics in go?
func (pool *fPool) fetch(url string) *ResultPromise {
pool.cacheLock.RLock()
if rp, pres := pool.cache[url]; pres {
pool.cacheLock.RUnlock()
return rp
}
pool.cacheLock.RUnlock()
pool.cacheLock.Lock()
if rp, pres := pool.cache[url]; pres {
pool.cacheLock.Unlock()
// Skip adding url if someone snuck it in between RUnlock an Lock
return rp
}
rp := newPromise()
pool.cache[url] = rp
pool.cacheLock.Unlock()
pool.c <- fetchWork{rp, url} // Expensive/atomic work
return rp
}
It's used for multiple maps of different types, for obvious reasons.
Maybe it's a poor solution?
Disclaimer: it's the same code from How to test unlikely concurrent scenarios?, sorry.
