此代码为了保障出错能够继续执行，类似于Java 的 try catch

defer func() {
        if panic_err := recover(); panic_err != nil {
            var buf [4096]byte
            n := runtime.Stack(buf[:], false)
            log.Errorf("xxx panic, panic_err:%+v, panic_stack:%s.", panic_err, string(buf[0:n]))
        }
    }()