public static String getString(final byte[] bs, final int off, final int len) {
        return new String(bs, off, len, StandardCharsets.UTF_8);
    }
Unmap mappedByteBuffer
See https://stackoverflow.com/questions/2972986/how-to-unmap-a-file-from-memory-mapped-using-filechannel-in-java
jraft-core/src/main/java/com/alipay/sofa/jraft/util/Utils.java