golang-error-handling

In Go a failure is a value handed back up the call stack; this is how to add context to it on the way up, recognise it at the top, and log it exactly once instead of three times.

WHEN TO USE

SCOPE

USE FOR

Wrap an error with fmt.Errorf and %w so the caller can unwrap the original cause.
Match a sentinel error with errors.Is or pull a typed error out of a chain with errors.As.
Fix a log-and-return violation where the same error gets logged twice.
Add samber/oops to a production error that needs a stack trace and tenant context.
Set up structured slog logging for errors so a log aggregator can group them cleanly.

NOT FOR

Not for the full samber/oops API or its builder patterns in depth.
Not for the broader slog handler ecosystem beyond basic structured logging.

This is a saved copy of the skill's SKILL.md instructions. It may differ from the upstream file or the version you install.

In this document (6)

Persona: You are a Go reliability engineer. You treat every error as an event that must either be handled or propagated with context — silent failures and duplicate logs are equally unacceptable.

Orchestration mode: Fan out the five category sub-agents described in the "Parallelizing Error Handling Audits" section (creation, wrapping, single-handling rule, panic/recover, structured logging) for auditing error handling across a large codebase, and consolidate their findings. On Claude Code, use ultracode to opt into multi-agent orchestration explicitly.

Modes:

Coding mode — writing new error handling code. Follow the best practices sequentially; optionally launch a background sub-agent to grep for violations in adjacent code (swallowed errors, log-and-return pairs) without blocking the main implementation.
Review mode — reviewing a PR's error handling changes. Focus on the diff: check for swallowed errors, missing wrapping context, log-and-return pairs, and panic misuse. Sequential.
Audit mode — auditing existing error handling across a codebase. Use up to 5 parallel sub-agents, each targeting an independent category (creation, wrapping, single-handling rule, panic/recover, structured logging).

Community default. A company skill that explicitly supersedes samber/cc-skills-golang@golang-error-handling skill takes precedence.

Go Error Handling Best Practices

This skill guides the creation of robust, idiomatic error handling in Go applications. Follow these principles to write maintainable, debuggable, and production-ready error code.

Best Practices Summary

Returned errors MUST always be checked — NEVER discard with _
Errors MUST be wrapped with context using fmt.Errorf("{context}: %w", err)
Error strings MUST be lowercase, without trailing punctuation
Use %w internally, %v at system boundaries to control error chain exposure
MUST use errors.Is for sentinel matching and errors.As/errors.AsType for typed chain inspection instead of direct comparison or bare type assertions. For Go 1.26+, prefer errors.AsType[T](err) when T implements error; use errors.As(err, &target) for Go <1.26 or for non-error interface targets.
SHOULD use errors.Join (Go 1.20+) to combine independent errors
Errors MUST be either logged OR returned, NEVER both (single handling rule)
Use sentinel errors for expected conditions, custom types for carrying data
NEVER use panic for expected error conditions — reserve for truly unrecoverable states
SHOULD use slog (Go 1.21+) for structured error logging — not fmt.Println or log.Printf
Use samber/oops for production errors needing stack traces, user/tenant context, or structured attributes
Log HTTP requests with structured middleware capturing method, path, status, and duration
Use log levels to indicate error severity
Never expose technical errors to users — translate internal errors to user-friendly messages, log technical details separately
Keep log grouping low-cardinality — at logging/APM boundaries, keep message templates stable and attach IDs, paths, line numbers, and counts as structured attributes. Error values may include useful operational context, but avoid putting high-cardinality data into the stable log message used for grouping.

Detailed Reference

Error Creation — How to create errors that tell the story: error messages should be lowercase, no punctuation, and describe what happened without prescribing action. Covers sentinel errors (one-time preallocation for performance), custom error types (for carrying rich context), and the decision table for which to use when.
Error Wrapping and Inspection — Why fmt.Errorf("{context}: %w", err) beats fmt.Errorf("{context}: %v", err) (chains vs concatenation). How to inspect chains with errors.Is, errors.As, and Go 1.26+ errors.AsType for type-safe error handling, and errors.Join for combining independent errors.
Error Handling Patterns and Logging — The single handling rule: errors are either logged OR returned, NEVER both (prevents duplicate logs cluttering aggregators). Panic/recover design, samber/oops for production errors, and slog structured logging integration for APM tools.

Parallelizing Error Handling Audits

When auditing error handling across a large codebase, use up to 5 parallel sub-agents — each targets an independent error category:

Sub-agent 1: Error creation — validate errors.New/fmt.Errorf usage, low-cardinality messages, custom types
Sub-agent 2: Error wrapping — audit %w vs %v, verify errors.Is/errors.As patterns
Sub-agent 3: Single handling rule — find log-and-return violations, swallowed errors, discarded errors (_)
Sub-agent 4: Panic/recover — audit panic usage, verify recovery at goroutine boundaries
Sub-agent 5: Structured logging — verify slog usage at error sites, check for PII in error messages

Cross-References

→ See samber/cc-skills-golang@golang-samber-oops for full samber/oops API, builder patterns, and logger integration
→ See samber/cc-skills-golang@golang-observability for structured logging setup, log levels, and request logging middleware
→ See samber/cc-skills-golang@golang-safety for nil interface trap and nil error comparison pitfalls
→ See samber/cc-skills-golang@golang-naming for error naming conventions (ErrNotFound, PathError)
→ See samber/cc-skills-golang@golang-continuous-integration skill for automated AI-driven code review in CI using these guidelines

References

This skill ships inside the Samber Golang Skills plugin.

Install just this skill

Run this outside your AI tool, using Node.js 22.20.0 or newer. Skills CLI 1.7.2 skips skill selection; prompts cancel installation without an interactive terminal. If choosing Project when asked about installation scope, open your project's folder before running this.

Install checklist

Check selected tools if a picker appears; Claude Code may be unchecked under Additional agents. ↑/↓ moves, Space toggles selections, Enter confirms.
Without a tool picker, check Installing to: for your intended tool. Stop if it names a different tool.
If asked, choose Symlink (Recommended) for shared files or Copy to all agents for separate copies; review the summary before confirming installation.
Install the find-skills skill? defaults to Yes, adding another skill for all projects. Choose No if you don't want that extra installation.

Skills CLI 1.7.2 sends install data to skills.sh by default, including the source, skill names, target tools and file details; GitHub sources are reported only when GitHub confirms the repository is public, while other remote sources can also be reported. Confirmed-public GitHub sources also trigger a security-audit request. Before installing, set the environment variable DO_NOT_TRACK=1 or DISABLE_TELEMETRY=1 to disable both.

npx skills add samber/cc-skills-golang --skill "golang-error-handling" --full-depth

After installing for Claude Code, open it in the installation project if you chose Project; Global makes the skill available across projects on this computer. Once Claude Code loads the skill, its description helps Claude decide when to use it.

If installation created a top-level skills folder that did not exist when your Claude Code session started, run /reload-skills in that session. Run it again after later changes in that folder.

Install the whole plugin

This route installs the Samber Golang Skills plugin package selected for your AI tool.

Add Samuel's marketplace, then install the plugin

Type both lines inside a Claude Code session, not at your shell prompt. The marketplace is a separate repository of Samuel Berthe's, samber/cc, which also lists his other plugins. The second line opens the details of cc-skills-golang, which carries this repository's 46 Go skills; pick one of the install options shown and Claude Code installs it.

01
```
/plugin marketplace add samber/cc
```
02
```
/plugin install cc-skills-golang@samber
```

Run it in your terminal. It copies the whole repository, with its 46 skills, into ~/.openclaw/skills/cc-skills-golang, OpenClaw's skills folder in your home folder. To install it for one OpenClaw workspace instead, Samuel gives ~/.openclaw/workspace/skills/cc-skills-golang as the folder.

git clone https://github.com/samber/cc-skills-golang.git ~/.openclaw/skills/cc-skills-golang

Run it in your terminal, not inside Gemini CLI; installing from GitHub needs git on your computer. It installs the repository, with its 46 skills, as a Gemini CLI extension. To update it later, run gemini extensions update cc-skills-golang.

gemini extensions install https://github.com/samber/cc-skills-golang

Run it in your terminal. It copies the whole repository, with its 46 skills, into ~/.cursor/skills/cc-skills-golang, Cursor's skills folder in your home folder.

git clone https://github.com/samber/cc-skills-golang.git  ~/.cursor/skills/cc-skills-golang

Type it in an interactive GitHub Copilot CLI session, not at your shell prompt. It installs the repository straight from GitHub as a plugin, with its 46 skills and no marketplace to add first.

/plugin install https://github.com/samber/cc-skills-golang

Run it in your terminal. It copies the whole repository, with its 46 skills, into ~/.agents/skills/cc-skills-golang in your home folder.

git clone https://github.com/samber/cc-skills-golang.git ~/.agents/skills/cc-skills-golang

Open plugin page ↗

What's inside

Files included with this skill.

View on GitHub

Same repository

golang-benchmark
Golang benchmarking, profiling, and performance measurement. Use when writing, running, or comparing Go benchmarks, profiling hot paths with pprof, interpreting CPU/memory/trace profiles, analyzing results with benchstat, setting up CI benchmark regression detection, or investigating production performance with Prometheus runtime metrics. Also use when the developer needs deep analysis on a specific performance indicator - this skill provides the measurement methodology, while samber/cc-skills-golang@golang-performance provides the optimization patterns.Read full description
golang-cli
Golang CLI application development. Use when building, modifying, or reviewing a Go CLI tool — especially for command structure, flag handling, configuration layering, version embedding, exit codes, I/O patterns, signal handling, shell completion, argument validation, and CLI unit testing. Also triggers when code uses cobra, viper, or urfave/cli. For cobra-specific APIs → See samber/cc-skills-golang@golang-spf13-cobra skill; for viper configuration layering → See samber/cc-skills-golang@golang-spf13-viper skill.Read full description
golang-code-style
Golang code style conventions — line length and breaking, variable declarations, control flow clarity, when comments help vs hurt. Use when writing or reviewing Go code, asking about style or clarity, or establishing project coding standards. Not for naming conventions (→ See samber/cc-skills-golang@golang-naming skill), linter configuration (→ See samber/cc-skills-golang@golang-lint skill), or doc comments (→ See samber/cc-skills-golang@golang-documentation skill).Read full description
golang-concurrency
Golang concurrency patterns. Use when writing or reviewing concurrent Go code involving goroutines, channels, select, locks, sync primitives, errgroup, singleflight, worker pools, or fan-out/fan-in pipelines. Also triggers when you detect goroutine leaks, race conditions, channel ownership issues, or need to choose between channels and mutexes.Read full description
golang-context
Idiomatic context.Context usage in Golang — propagation through API boundaries, cancellation, timeouts and deadlines, request-scoped values, context.WithoutCancel for background work outliving requests. Apply when designing context propagation across layers, debugging leaked or unexpired contexts, choosing between context.Background/TODO/WithoutCancel, or storing values in context. Not for code that merely accepts ctx as first parameter.Read full description
golang-continuous-integration
CI/CD pipeline configuration using GitHub Actions for Golang projects — testing, linting, SAST, security scanning, code coverage, Dependabot, Renovate, GoReleaser, code review automation, and release pipelines. Use when setting up or improving Go project CI, configuring GitHub Actions workflows, adding linters or security scanners, automating dependency updates, or adding quality gates.Read full description

Go Error Handling Best Practices

Best Practices Summary

Detailed Reference

Parallelizing Error Handling Audits

Cross-References

References

No requirements beyond installing this skill were found.

Install just this skill

Install the whole plugin

Add Samuel's marketplace, then install the plugin

What's inside

More skills

golang-benchmark

golang-cli

golang-code-style

golang-concurrency

golang-context

golang-continuous-integration