Ensure rule matcher is locked before updating

[jtescher]

Proposed changes

Lock CachedMatcher before rules are updated when HTTPMatcher refreshes to avoid concurrent map iteration and map write errors.

Checklist

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• I have added tests that prove my fix is effective or that my feature works
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[aeneasr]

I know why tests fail (issue with go modules) and will try to fix this on master in the next couple of days. Then you can rebase and if everything passes it will be merged :)

[aeneasr]

#160 resolved the build issue, could you rebase please? :)

[jtescher]

Rebased 👍

[aeneasr]

If you run make format the format task will pass too. This line is using spaces instead of tabs which causes the format checker to fail.

[jtescher]

Ok all checks are now passing

[aeneasr]

Awesome, thank you!