How to Run Go Tests in Parallel in CI

Go parallelism has two knobs: t.Parallel() runs tests within a package concurrently, and go test -p controls how many packages run at once.

Mark independent tests with t.Parallel(), then tune package-level concurrency with go test -p and per-package parallelism with -parallel.

Steps

• Call t.Parallel() at the top of tests that are independent.
• Set -p to bound how many packages run concurrently.
• Set -parallel to bound parallel tests within a package.

Test code

func TestThing(t *testing.T) {
    t.Parallel()
    // ... independent assertions
}

Terminal

go test -p 4 -parallel 8 ./...

Gotchas

• t.Parallel() tests share package-level state; guard globals or they will race.
• Run with -race in CI to catch data races that parallelism exposes.

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