go-errors

# Go Error Management Critical patterns for robust Go error handling. Covers sentinel errors, error wrapping with context, type/value checking, defer error patterns, and when to use panic vs return. ## When to Use This Skill - Writing error handling for any Go function - Reviewing code for ignored or swallowed errors - Using `errors.Is` / `errors.As` correctly - Deciding whether to wrap or not wrap an error - Handling errors inside defer statements ## How It Works 1. Identifies error handling anti-patterns (CRITICAL impact) 2. Explains the production consequences of each mistake 3. Shows correct error propagation and wrapping patterns 4. Covers the full error handling lifecycle ## Categories Covered 1. **Error Management** — sentinel values, wrapping, type checking, panicking, defer errors, ignored returns ## Present Results to User When identifying issues: ``` ❌ Found: Ignoring error return value 📍 Location: handlers/user.go:45 ⚠️ Impact: CRITICAL - Silent failures in production ✅ Fix: Check and handle the error explicitly [Show incorrect code] [Show correct code] [Explain why the fix matters] ``` ## Troubleshooting **When is it safe to ignore errors:** - `Close()` in defer after a successful write is sometimes acceptable — but log it - Use explicit `_ = f.Close()` to show the ignore is intentional, never silent **errors.Is vs errors.As:** - `errors.Is` checks for a specific error value (sentinel) - `errors.As` checks for a specific error type and unwraps the chain