go-data

name	go-data
description	Use this skill when working with Go slices, maps, integers, strings, range loops, or defer in loops to avoid common data type and control flow pitfalls.

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