NullPointerException in execInContainer for long running commands

Test case:

    @Test
    public void testExecInContainer() throws InterruptedException, IOException {
        try (GenericContainer<?> c = new GenericContainer<>(DockerImageName.parse("redis:3.0.2"))) {
            c.start();
            Container.ExecResult r = c.execInContainer("/bin/bash", "-c", "sleep 600");
        }
    }

After 3 minutes, I've got this exception (tested with testcontainers 1.16.0):

java.lang.NullPointerException
	at org.testcontainers.containers.ExecInContainerPattern.execInContainer(ExecInContainerPattern.java:85)
	at org.testcontainers.containers.ContainerState.execInContainer(ContainerState.java:235)
	at org.testcontainers.containers.ContainerState.execInContainer(ContainerState.java:226)

Note: I'm using DOCKER_HOST to execute on a Linux machine.

My real problem is: how do I execute a command which runs a long time? there seems to be an underlying socket timeout in docker-java, is it possible to increase this timeout?

Start with the failing test case in the issue and inspect ExecInContainerPattern.java:85, then follow the calls through ContainerState.java:226 and :235. Reproduce the long-running /bin/bash sleep command against the DOCKER_HOST setup and determine why it becomes a NullPointerException after three minutes. Done means long-running exec commands handle the timeout without that exception.