try can use automatic resource management

Author: Vincent Potucek

impl/maven-executor/src/main/java/org/apache/maven/cling/executor/forked/ForkedMavenExecutor.java

@@ -163,8 +163,10 @@ protected CountDownLatch pump(Process p, ExecutorRequest executorRequest) {
         CountDownLatch latch = new CountDownLatch(3);
         String suffix = "-pump-" + p.pid();
         Thread stdoutPump = new Thread(() -> {
-            try (OutputStream stdout = executorRequest.stdOut().orElse(OutputStream.nullOutputStream())) {
+            try {
+                OutputStream stdout = executorRequest.stdOut().orElse(OutputStream.nullOutputStream());
                 p.getInputStream().transferTo(stdout);
+                stdout.flush();
             } catch (IOException e) {
                 throw new UncheckedIOException(e);
             } finally {
@@ -174,8 +176,10 @@ protected CountDownLatch pump(Process p, ExecutorRequest executorRequest) {
         stdoutPump.setName("stdout" + suffix);
         stdoutPump.start();
         Thread stderrPump = new Thread(() -> {
-            try (OutputStream stderr = executorRequest.stdErr().orElse(OutputStream.nullOutputStream())) {
+            try {
+                OutputStream stderr = executorRequest.stdErr().orElse(OutputStream.nullOutputStream());
                 p.getErrorStream().transferTo(stderr);
+                stderr.flush();
             } catch (IOException e) {
                 throw new UncheckedIOException(e);
             } finally {
@@ -185,8 +189,10 @@ protected CountDownLatch pump(Process p, ExecutorRequest executorRequest) {
         stderrPump.setName("stderr" + suffix);
         stderrPump.start();
         Thread stdinPump = new Thread(() -> {
-            try (OutputStream in = p.getOutputStream()) {
+            try {
+                OutputStream in = p.getOutputStream();
                 executorRequest.stdIn().orElse(InputStream.nullInputStream()).transferTo(in);
+                in.flush();
             } catch (IOException e) {
                 throw new UncheckedIOException(e);
             } finally {