fix: N5ScalePyramidExporter use correct ThreadPool for progress

src/main/java/org/janelia/saalfeldlab/n5/ij/N5ScalePyramidExporter.java

@@ -41,6 +41,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.ThreadPoolExecutor;
@@ -284,6 +285,8 @@ public static enum DOWNSAMPLE_METHOD {
 
 	private final HashMap<Class<?>, N5MetadataWriter<?>> metadataWriters;
 
+	private ThreadPoolExecutor threadPool;
+
 	// consider something like this eventually
 	// private BiFunction<RandomAccessibleInterval<? extends
 	// NumericType<?>>,long[],RandomAccessibleInterval<?>> downsampler;
@@ -1201,14 +1204,16 @@ private <T extends RealType & NativeType, M extends N5Metadata> boolean write(
 
 		// Here, either allowing overwrite, or not allowing, but the dataset does not exist.
 		// use threadPool even for single threaded execution for progress monitoring
-		final ThreadPoolExecutor threadPool = new ThreadPoolExecutor(nThreads, nThreads, 0L, TimeUnit.MILLISECONDS,
+		threadPool = new ThreadPoolExecutor(nThreads, nThreads, 0L, TimeUnit.MILLISECONDS,
 				new LinkedBlockingQueue<Runnable>());
 		progressMonitor(threadPool);
 		N5Utils.save(image,
 				n5, dataset, chunkSize, compression,
-				Executors.newFixedThreadPool(nThreads));
+				threadPool);
 
 		writeMetadata(metadata, n5, dataset);
+		threadPool.shutdown();
+
 		return true;
 	}