private static boolean shouldCheck() {
		String noVersion = System.getenv().getOrDefault(Settings.ENV_NO_VERSION_CHECK, "false");
		if (Util.isOffline() || Util.isQuiet() || !noVersion.equalsIgnoreCase("false")) {
			return false;
		}
		try {
			Path versionFile = Settings.getCacheDir().resolve("version.txt");
			if (Files.isRegularFile(versionFile)) {
				FileTime ts = Files.getLastModifiedTime(versionFile);
				long diff = Duration.between(ts.toInstant(), Instant.now()).toDays();
				return diff > DELAY_DAYS;
			} else {
				Files.createFile(versionFile);
				return false;
			}
		} catch (IOException e) {
			// ignore
		}
		return true;
	}
Inform the user if the future returned a newer JBang version number, or
cancel the Future if it isn't done yet.
src/main/java/dev/jbang/util/VersionChecker.java