Golang Logging

Logging in Go (muonsoft/clog)

Package: github.com/muonsoft/clog (built on log/slog).

Context API (knowledge-db)

Prefer clog.Info(ctx, ...) / clog.Errorf(ctx, ...) over calling FromContext repeatedly unless you need the logger for many calls in one function.

Binding in middleware

logger := slog.Default().With(
    slog.String("request_method", r.Method),
    slog.String("request_url", r.URL.Path),
)
ctx := clog.NewContext(r.Context(), logger)
// pass ctx to handlers

slog attributes

slog.String("path", path)
slog.Int("count", n)
slog.Bool("ok", true)
slog.Any("detail", value)

Pass path, node id, job id, etc. as structured fields — not only inside the message string.

Logging errors

Use clog.Errorf with %w — not clog.Error + slog.String("error", err.Error()):

// Wrong — loses stack
clog.Error(ctx, "get node failed", slog.String("error", err.Error()))

// Correct
clog.Errorf(ctx, "get node failed: %w", err)

Error vs Warn

When unsure, prefer Error so real bugs are not hidden.

Handler pattern (from internal/api)

if errors.Is(err, kb.ErrNodeNotFound) {
    clog.Debug(r.Context(), "delete node: not found", "path", nodePath)
    writeError(w, http.StatusNotFound, "node not found")
    return
}
clog.Errorf(r.Context(), "delete node: %w", err)
writeError(w, http.StatusInternalServerError, err.Error())

Workers and loops

for task := range q.Tasks() {
    if err := worker.handle(ctx, task); err != nil {
        clog.Errorf(ctx, "handle task: %w", err)
    }
}

Rules

1. Do not log passwords, tokens, or session secrets.
2. Always pass context.Context as the first argument.
3. Business logic in internal/ uses clog only — do not add *slog.Logger fields to domain types; inject logger into context at the edge (HTTP middleware, main).
4. Errors: clog.Errorf with %w, or attributes via slog.* for non-error fields.
5. Do not duplicate attributes already on the request context logger.

Checklist

• github.com/muonsoft/clog used in internal/ and handlers
• Logger bound with clog.NewContext at request/worker boundary
• Failures logged with clog.Errorf and %w
• No sensitive data in log fields
• No ad-hoc slog.Default() in business packages

Source: strider2038/knowledge-db — distributed by TomeVault.