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