- use clearer method names, comments;
- define dtm usage info;
- determine action by switch-case instead of if-else, because only
os.Args[1] needs to be checked;
- use time layout '2006-01-02 15:04:05.999' to format milliseconds;
- change filenames dtmsvr/main.go to dtmsvr/dtmsvr.go;
- simplify code;
- use `()` to think less about operator precedence;
xxx