Fix InMemoryKache::getOrPut race condition in high concurrency

kache/src/commonMain/kotlin/com/mayakapps/kache/InMemoryKache.kt

@@ -164,14 +164,15 @@ public class InMemoryKache<K : Any, V : Any> internal constructor(
     override suspend fun getOrPut(key: K, creationFunction: suspend (key: K) -> V?): V? {
         get(key)?.let { return it }
 
-        creationMutex.withLock {
+        val deferred = creationMutex.withLock {
             if (creationMap[key] == null && map[key] == null) {
-                @Suppress("DeferredResultUnused")
                 internalPutAsync(key, creationFunction)
+            } else {
+                creationMap[key]
             }
         }
 
-        return get(key)
+        return deferred?.let { getFromCreation(key, it) } ?: get(key)
     }
 
     override suspend fun put(key: K, creationFunction: suspend (key: K) -> V?): V? =

kache/src/commonTest/kotlin/com/mayakapps/kache/InMemoryKacheTest.kt

@@ -686,4 +686,20 @@ class InMemoryKacheTest {
 
         assertEquals(0, kache.size)
     }
+
+    @Test
+    fun getOrPutHighConcurrency() = runTest {
+        // Regression test for https://github.com/MayakaApps/Kache/issues/239
+        // With more keys than maxSize, LRU eviction kicks in. In old code, a creation deferred
+        // could complete (on Dispatchers.Default) and get evicted between the creationMutex.withLock
+        // exit and the trailing get(key) call, returning null.
+        // Uses the real default creationScope (Dispatchers.Default) — testInMemoryKache overrides
+        // it to the single-threaded test dispatcher, which hides the race.
+        val kache = InMemoryKache<String, String>(maxSize = 100)
+
+        (0..20_000).forEach {
+            launch { assertNotNull(kache.getOrPut(it.toString()) { it.toString() }) }
+        }
+    }
+
 }