go-data

# Go Data Types & Control Flow Correct patterns for Go's built-in data types (slices, maps, integers), control structures (range loops, break, defer), and string handling (runes, UTF-8, conversions). ## When to Use This Skill - Working with slices and maps (initialization, capacity, memory leaks) - Iterating with range loops (variable capture, pointer reuse) - Handling integers (overflow, octal literals, floating point) - Manipulating strings (runes, trim, substring leaks) - Using defer inside loops ## How It Works 1. Identifies data type and control flow anti-patterns 2. Explains subtle Go semantics (nil vs empty slice, range variable reuse) 3. Shows correct implementations with working examples 4. Categorized by impact level ## Categories Covered 1. **Data Types** — slices, maps, integers, floating point, nil/empty slice 2. **Control Structures** — range loops, defer in loops, break, map iteration 3. **Strings** — runes, UTF-8, trim functions, substring memory leaks ## Present Results to User When identifying issues: ``` ❌ Found: Range loop variable captured by closure 📍 Location: handlers/batch.go:34 ⚠️ Impact: HIGH - All goroutines reference same variable ✅ Fix: Copy loop variable before passing to goroutine [Show incorrect code] [Show correct code] [Explain why the fix matters] ``` ## Troubleshooting **Nil vs empty slice confusion:** - Both have length 0, but nil slice marshals to `null` in JSON; empty slice marshals to `[]` - Use `var s []T` for nil slice, `s := []T{}` or `make([]T, 0)` for empty