When logging to a file, no logs are written if k6 is killed

[nadiamoe]

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Brief summary

If k6 is configured to log to a file and the process is killed in the middle of an execution, log messages produced by console.log instructions executed before the process were killed are lost, and the log file is empty.

k6 version

k6 v0.57.0 (go1.24.0, linux/amd64)

OS

Arch Linux

Docker version and image (if applicable)

No response

Steps to reproduce the problem

Take a simple script like this:

import { sleep } from 'k6'

export default function main() {
  console.log(`always log`);
  sleep(30);
}

And run it writing logs to a file:

k6 run --log-output=file=log-then-timeout.log log-then-timeout.js

After a few seconds, kill k6:

sleep 3; pkill -KILL k6

Realize that the log file is empty

nadia@Nadiarch 󱃾 curry-admin@Curry
14:44:21 /tmp/nadia $> wc browser-timeout.log
0 0 0 browser-timeout.log

Expected behaviour

I'd expect log-then-timeout.log to contain the always log string.

Actual behaviour

log-then-timeout.log is empty.