CI: sequence actions/checkout before actions/setup-go

[lukasschwab]

Changes

Reorders GitHub workflows using actions/checkout and actions/setup-go: run actions/checkout before actions/setup-go.

Running actions/checkout first checks out the go.sum file so the cache can hit. This matches the step-order demonstrated in the setup-go README:¹

steps:
  - uses: actions/checkout@v4
  - uses: actions/setup-go@v5

Motivation

The actions/setup-go build cache always misses because go.sum isn't present when the step runs. Here's the warning message and some timing notes ²

Warning: Restore cache failed: Dependencies file is not found in /home/runner/work/prebid-server/prebid-server. Supported file pattern: go.sum

Timestamp	Log	Note
17:08:45	Run ./validate.sh --nofmt --cov --race 10	Validate step starts.
17:08:50	go: downloading google.golang.org/genproto v0.0.0-20230410155749-daa745c078e1	Last dependency starts downloading.
17:12:56	ok github.com/prebid/prebid-server/v3 0.009s coverage: 3.1% of statements	First test log — four minutes later!

Validation

The first time this updated workflow runs (against this PR!) the setup-go step will still cache-miss, but it shouldn't emit the "Dependencies file is not found" log — the cache is just empty!

Subsequent runs should realize the speedup.

Footnotes

1. https://github.com/actions/setup-go?tab=readme-ov-file#basic ↩

2. https://github.com/prebid/prebid-server/actions/runs/16729524538/job/47353933940#step:2:16 ↩

[lukasschwab]

Unnecessary commentary...

For what it's worth, I think the race stage of validate.sh leaves a lot of room for optimization —

1. It takes ~1s per package even if there are no tests matching ^TestRace.*$; with 345 packages, that adds up despite parallelism.
2. I'm not sure the -count flag is necessary here; afaik, it doesn't impact whether or not a race is detected.

Haven't investigated deeply, but I wonder if this whole thing would be faster (and much simpler) with a single pass of go test -cover -race. Unfortunately, that turns up some race conditions in existing tests.

[lukasschwab]

Closing to clean up my inbox, but happy to reopen if it helps. cc @bsardo, @SyntaxNode, @VeronikaSolovei9, and @guscarreon (involved in a recent CI change #4251) — this would save a few minutes per CI run without changing the check logic at all.