Go's singleflight Package Prevents Cache Stampedes by Collapsing Duplicate Requests

Go's singleflight package, found in golang.org/x/sync/singleflight, ensures that when multiple goroutines request the same key simultaneously, only one actual function call is executed while all others wait and share the result. This directly addresses the cache stampede problem, where a hot key expiring can trigger thousands of simultaneous identical database calls. The package's Do method accepts a key and a function, executing the function once and broadcasting the result to all waiting callers, with a shared boolean indicating when a result was distributed to multiple waiters. Developers should treat returned values as immutable or return copies to avoid data races, since all waiting goroutines receive the exact same pointer. For context-aware cancellation, the DoChan method provides a channel-based alternative that allows callers to exit early without waiting for the in-flight request to complete.