private static void safeClose(File keyFile, OutputStream keyOut) {
        try {
            keyOut.close();
        } catch (IOException e) {
            if (logger.isWarnEnabled()) {
                logger.warn("Failed to close a file: " + keyFile, e);
            }
        }
    }
Deletes the generated X.509 certificate file and RSA private key file.
core/src/main/java/com/linecorp/armeria/internal/common/util/SelfSignedCertificate.java