private void close(HttpResponseWriter res, Closeable in) {
        close(in);
        res.close();
    }
Reads the content of {@code src} into {@code dst}.

@return the number of read bytes, or {@code -1} if reached at the end of the file

@throws IOException if failed to read the content
core/src/main/java/com/linecorp/armeria/server/file/StreamingHttpFile.java