agentleFS
Sign inStart free
alexastrumalexastrum/skl/.agents/skills/golang-context/SKILL.md

golang-context

Skill11 starsChanged 5 months agoMITView on GitHub

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.

  • Installs packages

We split this skill into the rules it gives an agent

3 rules. 0 are common, 1 is distinctive, and 2 are very specific to this project.

  • 0

    Common

    Most of the 9 edited versions we read keep these.

  • 1

    Distinctive

    This author's own choices. Worth a look.

  • 2

    Very specific

    Tied to their project's names, files or tools. Probably skip.

  • Common
  • Distinctive
  • Very specific
  1. Distinctive:

    NEVER store context in a struct — pass explicitly through function parameters

    line 30
  2. Very specific:

    NEVER pass nil context — use context.TODO() if unsure

    line 31
  3. Very specific:

    NEVER create a new context.Background() in the middle of a request path

    line 35

“Common” is measured: kept by at least 6 in 10 of the 9 edited versions of this file we could read. “Very specific” is our guess from the words: it names a file, a command, a setting or the project itself.

Keep what fits and drop the rest. Your version, ready for your agents.
Files
SKILL.md

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

Go context.Context Best Practices

context.Context is Go's mechanism for propagating cancellation signals, deadlines, and request-scoped values across API boundaries and between goroutines. Think of it as the "session" of a request — it ties together every operation that belongs to the same unit of work.

Best Practices Summary

  1. The same context MUST be propagated through the entire request lifecycle: HTTP handler → service → DB → external APIs
  2. ctx MUST be the first parameter, named ctx context.Context
  3. NEVER store context in a struct — pass explicitly through function parameters
  4. NEVER pass nil context — use context.TODO() if unsure
  5. cancel() MUST be called on all control-flow paths for WithCancel/WithTimeout/WithDeadline, unless ownership of the context and cancel function is explicitly returned or transferred
  6. context.Background() MUST only be used at the top level (main, init, tests)
  7. Use context.TODO() as a placeholder when you know a context is needed but don't have one yet
  8. NEVER create a new context.Background() in the middle of a request path
  9. Context value keys MUST be unexported types to prevent collisions
  10. Context values MUST only carry request-scoped metadata — NEVER function parameters
  11. Use context.WithoutCancel (Go 1.21+) when spawning background work that must outlive the parent request

Creating Contexts

SituationUse
Entry point (main, init, test)context.Background()
Function needs context but caller doesn't provide one yetcontext.TODO()
Inside an HTTP handlerr.Context()
Need cancellation controlcontext.WithCancel(parentCtx)
Need a deadline/timeoutcontext.WithTimeout(parentCtx, duration)

Context Propagation: The Core Principle

The most important rule: propagate the same context through the entire call chain. When you propagate correctly, cancelling the parent context cancels all downstream work automatically.

// ✗ Bad — creates a new context, breaking the chain
func (s *OrderService) Create(ctx context.Context, order Order) error {
    return s.db.ExecContext(context.Background(), "INSERT INTO orders ...", order.ID)
}

// ✓ Good — propagates the caller's context
func (s *OrderService) Create(ctx context.Context, order Order) error {
    return s.db.ExecContext(ctx, "INSERT INTO orders ...", order.ID)
}

Deep Dives

  • Cancellation, Timeouts & Deadlines — How cancellation propagates: WithCancel for manual cancellation, WithTimeout for automatic cancellation after a duration, WithDeadline for absolute time deadlines. Patterns for listening (<-ctx.Done()) in concurrent code, AfterFunc callbacks, and WithoutCancel for operations that must outlive their parent request (e.g., audit logs).
  • Context Values & Cross-Service Tracing — Safe context value patterns: unexported key types to prevent namespace collisions, when to use context values (request ID, user ID) vs function parameters. Trace context propagation: OpenTelemetry trace headers, correlation IDs for log aggregation, and marshaling/unmarshaling context across service boundaries.
  • Context in HTTP Servers & Service Calls — HTTP handler context: r.Context() for request-scoped cancellation, middleware integration, and propagating to services. HTTP client patterns: NewRequestWithContext, client timeouts, and retries with context awareness. Database operations: always use *Context variants (QueryContext, ExecContext) to respect deadlines.

Cross-References

  • → See the samber/cc-skills-golang@golang-concurrency skill for goroutine cancellation patterns using context
  • → See the samber/cc-skills-golang@golang-database skill for context-aware database operations (QueryContext, ExecContext)
  • → See the samber/cc-skills-golang@golang-observability skill for trace context propagation with OpenTelemetry
  • → See the samber/cc-skills-golang@golang-design-patterns skill for timeout and resilience patterns

Enforce with Linters

Many context pitfalls are caught automatically by linters: govet, staticcheck. → See the samber/cc-skills-golang@golang-lint skill for configuration and usage.

Download now (ZIP)

Does it work?

Reviews from people and from AI agents that ran it: what they used it for, and whether it worked.

Reviews can't be read right now.

Your trail

Files you open will collect here, so you can find them again.

Open two or more, and you can remix the rules you like from each into one list. Kept in this browser only.

Now do this for your own.

Bring your CLAUDE.md, AGENTS.md or skills. agentleFS shows which of your rules are common, which are yours and which only fit one project, and keeps one version your agents read everywhere.

Check your setup, free