feat: add concurrency option to parallelize package loading

[kruskall]

This PR adds support for running package loading in parallel due to gosec.load being a major bottleneck for big projects.

The concurrency option defaults to the number of available CPUs and tests are using a concurrency value of 1.

Benchmarks:

Benchmarks of a couple of GitLab projects using hyperfine:

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Gitlab Pages:

before:

Benchmark 1: /path/to/gosec -exclude-generated ./...
Time (mean ± σ):     11.384 s ±  0.227 s    [User: 28.443 s, System: 8.731 s]
Range (min … max):   10.974 s … 11.793 s    10 runs

Warning: Ignoring non-zero exit code.

after:

Benchmark 1: /path/to/gosec -exclude-generated ./...
Time (mean ± σ):      2.292 s ±  0.078 s    [User: 23.965 s, System: 8.732 s]
Range (min … max):    2.230 s …  2.469 s    10 runs

Warning: Ignoring non-zero exit code.

Gitaly

before:

Benchmark 1: /path/to/gosec -exclude-generated ./...
Time (mean ± σ):     27.442 s ±  0.710 s    [User: 75.289 s, System: 20.270 s]
Range (min … max):   26.601 s … 28.497 s    10 runs

Warning: Ignoring non-zero exit code.

after:

Benchmark 1: /path/to/gosec -exclude-generated ./...
Time (mean ± σ):      5.953 s ±  1.047 s    [User: 67.921 s, System: 20.703 s]
Range (min … max):    5.237 s …  8.658 s    10 runs

Warning: Ignoring non-zero exit code.

[ccojocar]

@kruskall Thanks for this improvement. I'll have a closer look at it soon. Please could you add some unit tests where the concurrency is more than 1. I'll like to see that the concurrent case is covered by test.

[ccojocar]

Check cannot be made concurrent due to the shared state in the analyser. Sorry for my recommendation to make it concurrent.

[kruskall]

@kruskall Thanks for this improvement. I'll have a closer look at it soon. Please could you add some unit tests where the concurrency is more than 1. I'll like to see that the concurrent case is covered by test.

@ccojocar Thank you for the feedback! I've added a test with a concurrency value of 32, a few more comments and made sure a goroutine would stop if there are no jobs left. Back to you 🏓

[ccojocar]

Thanks for fixing the review comments. It looks good now!