Fix session leak when context canceled during async creation

internal/pool/pool.go

@@ -270,7 +270,18 @@ func makeAsyncCreateItemFunc[PT ItemConstraint[T], T any]( //nolint:funlen
 					return
 				}
 
-				_ = p.putItem(createCtx, newItem)
+				// Caller canceled before receiving the item, need to remove from index and close
+				p.mu.WithLock(func() {
+					delete(p.index, newItem)
+				})
+
+				closeCtx := createCtx
+				if t := p.config.closeTimeout; t > 0 {
+					var cancel context.CancelFunc
+					closeCtx, cancel = context.WithTimeout(closeCtx, t)
+					defer cancel()
+				}
+				p.config.closeItemFunc(closeCtx, newItem)
 			}
 		}()
 

internal/pool/pool_test.go

@@ -1220,5 +1220,91 @@
 				_ = p.putItem(context.Background(), item)
 			})
 		})
+		t.Run("ContextCanceledDuringCreate", func(t *testing.T) {
+			// This test validates the fix for the session leak bug where
+			// context cancellation during session creation would cause the
+			// session to be added to the pool index but never properly tracked
+			var (
+				createStarted   = make(chan struct{})
+				allowCreateDone = make(chan struct{})
+				itemsCreated    atomic.Int32
+				itemsClosed     atomic.Int32
+			)
+			p := New(rootCtx,
+				WithLimit[*testItem, testItem](2),
+				WithTrace[*testItem, testItem](defaultTrace),
+				WithCreateItemFunc[*testItem, testItem](func(ctx context.Context) (*testItem, error) {
+					close(createStarted)
+					<-allowCreateDone
+					if ctx.Err() != nil {
+						return nil, ctx.Err()
+					}
+					itemsCreated.Add(1)
+					return &testItem{
+						onClose: func() error {
+							itemsClosed.Add(1)
+							return nil
+						},
+						onIsAlive: func() bool {
+							return true
+						},
+					}, nil
+				}),
+			)
+
+			// Start creating an item but cancel context before creation completes
+			ctx, cancel := context.WithCancel(rootCtx)
+			errCh := make(chan error, 1)
+			itemCh := make(chan *testItem, 1)
+			go func() {
+				item, err := p.createItemFunc(ctx)
+				itemCh <- item
+				errCh <- err
+			}()
+
+			// Wait for creation to start
+			<-createStarted
+
+			// Cancel the context while creation is in progress
+			cancel()
+
+			// Allow creation to complete
+			close(allowCreateDone)
+
+			// Wait for the create call to return
+			item := <-itemCh
+			err := <-errCh
+
+			// Give time for the goroutine to clean up
+			time.Sleep(100 * time.Millisecond)
+
+			if err == nil && item != nil {
+				// Case 1: Item was created successfully before context was checked
+				// This is valid - the item should be in the pool
+				stats := p.Stats()
+				require.Equal(t, 1, stats.Index, "item should be in pool index")
+				// Clean up - close the item
+				_ = item.Close(rootCtx)
+			} else {
+				// Case 2: Context was canceled before item creation
+				// The item should have been closed and not added to pool
+				require.Error(t, err)
+				require.ErrorIs(t, err, context.Canceled)
+
+				// If item was created, it should have been closed
+				if itemsCreated.Load() > 0 {
+					require.Equal(t, int32(1), itemsClosed.Load(), "created item should have been closed")
+				}
+
+				// Verify pool stats show no leaked sessions
+				stats := p.Stats()
+				require.Equal(t, 0, stats.Index, "pool index should be empty when item not returned")
+				require.Equal(t, 0, stats.Idle, "pool idle should be empty")
+			}
+
+			// In both cases, createInProgress should be 0
+			stats := p.Stats()
+			require.Equal(t, 0, stats.CreateInProgress, "no create should be in progress")
+		})
 	})
 }