Fix some data races

[knightpp]

What does this do?

I noticed data races in my codebase, turns out the issue is not in my code. So, I fixed it here.

Which issue(s) does this PR fix/relate to?

List any changes that modify/break current functionality

Tests pass

Have you included tests for your changes?

No

Did you document any new/modified functionality?

• Updated example_test.go
• Updated README.md

Notes

I've not tested it, only run go test ./.... Feel free to close if you feel that this PR is not appropriate.

[JohnRoesler]

Thanks for the contribution!

Could you share the data races you saw? The tests are failing on this PR because of new data races that weren't previously there, so this doesn't seem to be solving the problem.

[knightpp]

I cannot provide code with the issue, but the data race happens when getCurrentJob() sets an element in the map and runJobs() tries to iterate over the map.

[knightpp]

Also, the fix should probably be applied to every place where jobsMap() is used in for range loop.

[JohnRoesler]

#589 solved this issue