Breaking signature: Allow context propagation (but without cancel pro…

…pagation) in all replaceFn call paths

This allows passing arbitrary context values such as tracing contexts into replaceFn, which should help distributed tracing ecosystem.

cache.go

@@ -127,7 +127,7 @@ retry:
 			cl := &call[V]{}
 			cl.wg.Add(1)
 			c.calls[key] = cl
-			go c.set(context.Background(), cl, key) // Use empty context so as not to be cancelled by the original context
+			go c.set(context.WithoutCancel(ctx), cl, key)
 		}
 		c.stats.GraceHits++
 		c.mu.Unlock()
@@ -187,7 +187,7 @@ func (c *cache[K, V]) GetIfExists(key K) (v V, ok bool) {
 }
 
 // Notify instructs the cache to retrieve value for key if value does not exist or is stale, in a non-blocking manner.
-func (c *cache[K, V]) Notify(key K) {
+func (c *cache[K, V]) Notify(ctx context.Context, key K) {
 	// Record time as soon as Get is called *before acquiring the lock* - this maximizes the reuse of values
 	calledAt := monoTimeNow()
 	c.mu.Lock()
@@ -205,7 +205,7 @@ func (c *cache[K, V]) Notify(key K) {
 		cl := &call[V]{}
 		cl.wg.Add(1)
 		c.calls[key] = cl
-		go c.set(context.Background(), cl, key) // Use empty context so as not to be cancelled by the original context
+		go c.set(context.WithoutCancel(ctx), cl, key)
 	}
 	c.mu.Unlock()
 }

cache_test.go

@@ -456,7 +456,7 @@ func TestCache_Notify(t *testing.T) {
 			t0 := time.Now()
 
 			// Notify value retrieval - this should launch goroutine in background
-			cache.Notify("k1")
+			cache.Notify(context.Background(), "k1")
 			// Test that value is still not here
 			_, ok := cache.GetIfExists("k1")
 			assert.False(t, ok)
@@ -477,7 +477,7 @@ func TestCache_Notify(t *testing.T) {
 			assert.EqualValues(t, 1, cnt)
 
 			// t=750ms, notify once again - this should do *nothing*
-			cache.Notify("k1")
+			cache.Notify(context.Background(), "k1")
 
 			time.Sleep(750 * time.Millisecond)
 			// t=1500ms, assert that value was replaced only once