Modernize Go syntax: replace deprecated rand.Seed and interface{}

[Copilot]

Updates code to use modern Go idioms, removing deprecated patterns that were flagged in Go 1.18+ and 1.20+.

Changes

• level_9.go: Replace deprecated rand.Seed() with rand.New(rand.NewSource())

  // Before
  func main() {
      rand.Seed(111009)
      // ... use rand.Intn()
  }
  
  // After
  var rng = rand.New(rand.NewSource(111009))
  func main() {
      // ... use rng.Intn()
  }

• level_8.go, solutions.txt: Replace interface{} with any type alias

  // Before
  func startup(seq interface{}) bool
  
  // After  
  func startup(seq any) bool

• Add .gitignore: Prevent Go build artifacts and cache from being committed

Original prompt

Can you please see if any code should be updated to reflect changes in Go's syntax or file structure?

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[andybrewer]

@copilot Great! And can you please check if the level problems and solutions are all still valid? I heard some reports that the level with the race condition wasn't resolving properly even with the proposed solution.

[Copilot]

@copilot Great! And can you please check if the level problems and solutions are all still valid? I heard some reports that the level with the race condition wasn't resolving properly even with the pr...

I've validated all 12 levels and their solutions - everything works correctly!

Level 9 (Race Condition) - The Reported Issue:

• ✅ The mutex solution from solutions.txt correctly fixes the race condition
• Tested with Go's race detector: WITHOUT mutex shows DATA RACE, WITH mutex shows NO RACES
• The output order varies between runs (e.g., "purple, green, blue..." vs "purple, blue, red...") - this is expected behavior for concurrent code where goroutines race to acquire the mutex
• The puzzle objective is "Fix the race condition", not achieve deterministic ordering

All Other Levels (1-8, 10-12):

• ✅ All solutions tested and working correctly
• ✅ Level 8 works perfectly with the modernized any type
• ✅ No breaking changes from the syntax updates

The modernized Go syntax (any instead of interface{}, rand.New() instead of rand.Seed()) is fully compatible with all levels and solutions.