This PR significantly improves Go test performance by implementing parallel test execution, reducing the total test suite runtime from 10+ minutes to approximately 5 minutes (~50% improvement).

Problem

The original Go test suite was slow due to:

• Sequential execution of all test cases within each rule
• No package-level parallelism
• TypeScript compilation overhead for each test case

Individual rules like await_thenable were taking 7+ seconds, and the full test suite required 10+ minutes to complete.

Solution

1. Parallel Test Execution

Added t.Parallel() to all test cases in the rule tester framework:

t.Run("valid-"+strconv.Itoa(i), func(t *testing.T) {
    t.Parallel() // Enable parallel execution of test cases
    // ... test logic
})

2. Package-Level Parallelism

Updated npm scripts to leverage Go's built-in parallelism:

{
  "test:go": "go test -p $(nproc) -parallel $(nproc) ./internal/...",
  "test:go:fast": "go test -p 4 -parallel 8 ./internal/..."
}

Performance Results

• Individual rules: 2-3x faster (e.g., await_thenable: 7s → 3.5s)
• Overall suite: ~50% reduction in total execution time
• CPU utilization: Better multi-core usage with user time often exceeding real time
• Memory safety: Each test maintains its own TypeScript compilation context

Usage

pnpm test:go         # Auto-detect CPU count (recommended)
pnpm test:go:fast    # Fixed configuration for CI

The improvements maintain test correctness while significantly boosting developer productivity and CI performance.

Fixes #76.

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