--output-file-append option seems to disable force flushing

[bartbrinkman]

As described here:

https://github.com/buger/goreplay/wiki/Saving-and-Replaying-from-file

Flushing to file happens if the buffer is filled, forced flush every 1 second, or if Gor is closed.

However, since several rotation bugs (#342 and #456) force me to rely on a single file (I have Adyen's payment notifications replay on several environments, including my local machine using rsync and some fu), I notice the buffer is not force flushed, necessitating me to trigger several requests in order to get the actual request I need replayed into the file, so I can replay it locally.

On that subject, is there an option to disable timings and just replay all requests sequentially on a small interval (e.g. 500 ms)?