Golang Samber Oops Agent Skill

Persona: You are a Go engineer who treats errors as structured data. Every error carries enough context — domain, attributes, trace — for an on-call engineer to diagnose the problem without asking the developer.

samber/oops Structured Error Handling

samber/oops is a drop-in replacement for Go's standard error handling that adds structured context, stack traces, error codes, public messages, and panic recovery. Variable data goes in .With() attributes (not the message string), so APM tools (Datadog, Loki, Sentry) can group errors properly. Unlike the stdlib approach (adding slog attributes at the log site), oops attributes travel with the error through the call stack.

Why use samber/oops

Standard Go errors lack context — you see connection failed but not which user triggered it, what query was running, or the full call stack. samber/oops provides:

• Structured context — key-value attributes on any error
• Stack traces — automatic call stack capture
• Error codes — machine-readable identifiers
• Public messages — user-safe messages separate from technical details
• Low-cardinality messages — variable data in .With() attributes, not the message string, so APM tools group errors properly

This skill is not exhaustive. Please refer to library documentation and code examples for more information. For Go package docs, symbols, versions, importers, and known vulnerabilities, → See samber/cc-skills-golang@golang-pkg-go-dev skill (godig) — prefer it over Context7 for Go package facts. To navigate this library's usage in your own code (definitions, call sites, diagnostics), → See samber/cc-skills-golang@golang-gopls skill (gopls). Context7 remains a fallback for docs not indexed on pkg.go.dev.

Core pattern: Error builder chain

All oops errors use a fluent builder pattern:

err := oops.
    In("user-service").           // domain/feature
    Tags("database", "postgres").  // categorization
    Code("network_failure").       // machine-readable identifier
    User("user-123", "email", "[email protected]").  // user context
    With("query", query).          // custom attributes
    Errorf("failed to fetch user: %s", "timeout")

Terminal methods:

• .Errorf(format, args...) — create a new error
• .Wrap(err) — wrap an existing error
• .Wrapf(err, format, args...) — wrap with a message
• .Join(err1, err2, ...) — combine multiple errors
• .Recover(fn) / .Recoverf(fn, format, args...) — convert panic to error

Error builder methods

| Methods | Use case |

| --- | --- |

| .With("key", value) | Add custom key-value attribute (lazy func() any values supported) |

| .WithContext(ctx, "key1", "key2") | Extract values from Go context into attributes (lazy values supported) |

| .In("domain") | Set the feature/service/domain |

| .Tags("auth", "sql") | Add categorization tags (query with err.HasTag("tag")) |

| .Code("iam_authz_missing_permission") | Set machine-readable error identifier/slug |

| .Public("Could not fetch user.") | Set user-safe message (separate from technical details) |

| .Hint("Runbook: https://doc.acme.org/doc/abcd.md") | Add debugging hint for developers |

| .Owner("team/slack") | Identify responsible team/owner |

| .User(id, "k", "v") | Add user identifier and attributes |

| .Tenant(id, "k", "v") | Add tenant/organization context and attributes |

| .Trace(id) | Add trace / correlation ID (default: ULID) |

| .Span(id) | Add span ID representing a unit of work/operation (default: ULID) |

| .Time(t) | Override error timestamp (default: time.Now()) |

| .Since(t) | Set duration based on time since t (exposed via err.Duration()) |

| .Duration(d) | Set explicit error duration |

| .Request(req, includeBody) | Attach *http.Request (optionally including body) |

| .Response(res, includeBody) | Attach *http.Response (optionally including body) |

| oops.FromContext(ctx) | Start from an OopsErrorBuilder stored in a Go context |

Common scenarios

Database/repository layer

func (r *UserRepository) FetchUser(id string) (*User, error) {
    query := "SELECT * FROM users WHERE id = $1"
    row, err := r.db.Query(query, id)
    if err != nil {
        return nil, oops.
            In("user-repository").
            Tags("database", "postgres").
            With("query", query).
            With("user_id", id).
            Wrapf(err, "failed to fetch user from database")
    }
    // ...
}

HTTP handler layer

func (h *Handler) CreateUser(w http.ResponseWriter, r *http.Request) {
    userID := getUserID(r)

    err := h.service.CreateUser(r.Context(), userID)
    if err != nil {
        err = oops.
            In("http-handler").
            Tags("endpoint", "/users").
            Request(r, false).
            User(userID).
            Wrapf(err, "create user failed")
        http.Error(w, oops.GetPublic(err, "Internal server error"), http.StatusInternalServerError)
        return
    }

    w.WriteHeader(http.StatusCreated)
}

Service layer with reusable builder

func (s *UserService) CreateOrder(ctx context.Context, req CreateOrderRequest) error {
    builder := oops.
        In("order-service").
        Tags("orders", "checkout").
        Tenant(req.TenantID, "plan", req.Plan).
        User(req.UserID, "email", req.UserEmail)

    product, err := s.catalog.GetProduct(ctx, req.ProductID)
    if err != nil {
        return builder.
            With("product_id", req.ProductID).
            Wrapf(err, "product lookup failed")
    }

    if product.Stock < req.Quantity {
        return builder.
            Code("insufficient_stock").
            Public("Not enough items in stock.").
            With("requested", req.Quantity).
            With("available", product.Stock).
            Errorf("insufficient stock for product %s", req.ProductID)
    }

    return nil
}

Error wrapping best practices

DO: Wrap directly, no nil check needed

// ✓ Good — Wrap returns nil if err is nil
return oops.Wrapf(err, "operation failed")

// ✗ Bad — unnecessary nil check
if err != nil {
    return oops.Wrapf(err, "operation failed")
}
return nil

DO: Add context at each layer

Each architectural layer SHOULD add context via Wrap/Wrapf — at least once per package boundary (not necessarily at every function call).

// ✓ Good — each layer adds relevant context
func Controller() error {
    return oops.In("controller").Trace(traceID).Wrapf(Service(), "user request failed")
}

func Service() error {
    return oops.In("service").With("op", "create_user").Wrapf(Repository(), "db operation failed")
}

func Repository() error {
    return oops.In("repository").Tags("database", "postgres").Errorf("connection timeout")
}

DO: Keep error messages low-cardinality

Error messages MUST be low-cardinality for APM aggregation. Interpolating variable data into the message breaks grouping in Datadog, Loki, Sentry.

// ✗ Bad — high-cardinality, breaks APM grouping
oops.Errorf("failed to process user %s in tenant %s", userID, tenantID)

// ✓ Good — static message + structured attributes
oops.With("user_id", userID).With("tenant_id", tenantID).Errorf("failed to process user")

Panic recovery

oops.Recover() MUST be used in goroutine boundaries. Convert panics to structured errors:

func ProcessData(data string) (err error) {
    return oops.
        In("data-processor").
        Code("panic_recovered").
        Hint("Check input data format and dependencies").
        With("input_data", data).
        Recover(func() {
            riskyOperation(data)
        })
}

Accessing error information

samber/oops errors implement the standard error interface. Access additional info:

if oopsErr, ok := err.(oops.OopsError); ok {
    fmt.Println("Code:", oopsErr.Code())
    fmt.Println("Domain:", oopsErr.Domain())
    fmt.Println("Tags:", oopsErr.Tags())
    fmt.Println("Context:", oopsErr.Context())
    fmt.Println("Stacktrace:", oopsErr.Stacktrace())
}

// Get public-facing message with fallback
publicMsg := oops.GetPublic(err, "Something went wrong")

Output formats

fmt.Printf("%+v\n", err)       // verbose with stack trace
bytes, _ := json.Marshal(err)  // JSON for logging
slog.Error(err.Error(), slog.Any("error", err))  // slog integration

Context propagation

Carry error context through Go contexts:

func middleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        builder := oops.
            In("http").
            Request(r, false).
            Trace(r.Header.Get("X-Trace-ID"))

        ctx := oops.WithBuilder(r.Context(), builder)
        next.ServeHTTP(w, r.WithContext(ctx))
    })
}

func handler(ctx context.Context) error {
    return oops.FromContext(ctx).Tags("handler", "users").Errorf("something failed")
}

For assertions, configuration, and additional logger examples, see Advanced patterns.

References

• github.com/samber/oops
• pkg.go.dev/github.com/samber/oops

Cross-References

• → See samber/cc-skills-golang@golang-error-handling skill for general error handling patterns
• → See samber/cc-skills-golang@golang-observability skill for logger integration and structured logging