Error handling

Skill saifoelloh/golang-best-practices-skill/error-handling

Production-ready Go code review skill for AI agents based on authoritative sources

Install

npx -y skills add saifoelloh/golang-best-practices-skill --skill error-handling

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Unified Go + GORM + PostgreSQL error handling review. Covers error wrapping, context propagation, PostgreSQL error codes (23505, 40001), errors.Is/As mapping, and retry logic. Ensures proper error chains and robust database failure recovery.

The file declares its own license as MIT. That is the author’s claim about this one file, and it is not the same thing as the license GitHub reports for the repository, which is listed with the other numbers below.

SKILL.md

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Error Handling (Unified Go & DB)

Expert-level review for error handling in Go services using GORM and PostgreSQL. Ensures errors are correctly identified, preserved via wrapping, mapped to domain errors, and retried where appropriate.

When to Apply

Use this skill when:

Reviewing general Go error propagation and context usage
Debugging database errors (e.g., duplicate keys, serialization failures)
Auditing error wrapping with %w vs %v
Ensuring correct use of errors.Is / errors.As
Adding retry logic for serializable transactions or deadlocks

Rule Categories

Priority	Count	Focus
CRITICAL	6	error chains, context leaks, PgError mapping, retries
HIGH	6	propagation, Is/As usage, RowsAffected, deadlock detection
MEDIUM	2	sentinel errors, structured logging

Rules Covered (14 total)

Critical Issues (6)

critical-error-wrapping — Use %w, not %v, to preserve error chains
critical-context-leak — Always defer cancel() after context creation
critical-error-shadow — Don't shadow err in nested scopes
critical-errors-is-as — Use errors.Is/As for DB and wrapped errors
critical-pg-error-mapping — Map Postgres codes to domain errors at repo boundary
critical-serialization-retry — Retry transactions on 40001 serialization failure

High-Impact Patterns (6)

high-context-propagation — Propagate context through the call chain
high-error-is-as — Prescriptive rule for using Is/As over string matching
high-interface-nil — Check for nil in interfaces correctly
high-rows-affected — Check RowsAffected after Update/Delete
high-wrap-with-context — Wrap DB errors with operation context
high-deadlock-detection — Handle 40P01 deadlocks as retryable

Medium Improvements (2)

medium-sentinel-error-usage — Use sentinel errors for stable categories
medium-structured-logging — Log DB/Go errors with structured fields

Trigger Phrases

"Review error handling"
"Debug this DB error"
"23505 / 40001 / 40P01"
"Check for context leaks"
"Review error chains"
"Transaction retry"
"ErrRecordNotFound"

Output Format

## Critical Issues Found: X

### [Rule ID] (Line Y)
**Issue**: Description
**Impact**: Context leak / Lost chain / Data inconsistency
**Fix**: Suggested code
**Example**:
```go
// Corrected code


## Related Skills
- [gorm-query-patterns](../gorm-query-patterns/SKILL.md) — For `.Error` check safety
- [concurrency-safety](../concurrency-safety/SKILL.md) — For context timeout patterns