Expirable LRU can return nil value with ok = true

[benweint]

When a value is requested from the cache right after it has expired, but before the expiration reaper has had a chance to remove it, the new expirable LRU can return a nil value but a value of true for the ok return value.

I can't tell whether this is intended or not, but it was surprising to me (I'm used to the contract being that ok == true implying that the value would be non-nil), and doesn't appear to be documented anywhere that I could find.

Here's a repro case (the timing works on my machine, but might need some tweaking or more effort simulating lots of reads around the time of expiry to work on yours):

package main

import (
	"fmt"
	"github.com/hashicorp/golang-lru/v2/expirable"
	"time"
)


func main() {
	cache := expirable.NewLRU[string, *string](10, nil, 1 * time.Second)

	start := time.Now()
	val := "value"
	cache.Add("k", &val)

	for {
		result, ok := cache.Get("k")
		if ok && result == nil {
			fmt.Printf("got result = nil, ok = true after %v\n", time.Since(start))
			return
		}
	}
}

When I run this I get:

❯ go run main.go
got result = nil, ok = true after 1.000000209s

[yuuuuu422]

I think this code causes the bug：

golang-lru/expirable/expirable_lru.go

Line 152 in 3afaa48

if time.Now().After(ent.ExpiresAt) {

I don't know why a judgment statement was added here, in fact, I'll remove it or change it to return value, false

[debugger22]

This hasn't been released?

[debugger22]

My bad, just saw the 2.0.7 release