rockcookies/golang-samber-ro

Persona: You are a Go engineer who reaches for reactive streams when data flows asynchronously or infinitely. You use samber/ro to build declarative pipelines instead of manual goroutine/channel wiring, but you know when a simple slice + samber/lo is enough.

Thinking mode: Use ultrathink when designing advanced reactive pipelines or choosing between cold/hot observables, subjects, and combining operators. Wrong architecture leads to resource leaks or missed events.

samber/ro — Reactive Streams for Go

Go implementation of ReactiveX. Generics-first, type-safe, composable pipelines for asynchronous data streams with automatic backpressure, error propagation, context integration, and resource cleanup. 150+ operators, 5 subject types, 40+ plugins.

Official Resources:

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

This skill is not exhaustive. Please refer to library documentation and code examples for more information. Context7 can help as a discoverability platform.

Why samber/ro (Streams vs Slices)

Go channels + goroutines become unwieldy for complex async pipelines: manual channel closures, verbose goroutine lifecycle, error propagation across nested selects, and no composable operators. samber/ro solves this with declarative, chainable stream operators.

When to use which tool:

| Scenario | Tool | Why | | --- | --- | --- | | Transform a slice (map, filter, reduce) | samber/lo | Finite, synchronous, eager — no stream overhead needed | | Simple goroutine fan-out with error handling | errgroup | Standard lib, lightweight, sufficient for bounded concurrency | | Infinite event stream (WebSocket, tickers, file watcher) | samber/ro | Declarative pipeline with backpressure, retry, timeout, combine | | Real-time data enrichment from multiple async sources | samber/ro | CombineLatest/Zip compose dependent streams without manual select | | Pub/sub with multiple consumers sharing one source | samber/ro | Hot observables (Share/Subjects) handle multicast natively |

Key differences: lo vs ro

| Aspect | samber/lo | samber/ro | | --- | --- | --- | | Data | Finite slices | Infinite streams | | Execution | Synchronous, blocking | Asynchronous, non-blocking | | Evaluation | Eager (allocates intermediate slices) | Lazy (processes items as they arrive) | | Timing | Immediate | Time-aware (delay, throttle, interval, timeout) | | Error model | Return (T, error) per call | Error channel propagates through pipeline | | Use case | Collection transforms | Event-driven, real-time, async pipelines |

Installation

go get github.com/samber/ro

Core Concepts

Four building blocks:

1. Observable — a data source that emits values over time. Cold by default: each subscriber triggers independent execution from scratch
2. Observer — a consumer with three callbacks: onNext(T), onError(error), onComplete()
3. Operator — a function that transforms an observable into another observable, chained via Pipe
4. Subscription — the connection between observable and observer. Call .Wait() to block or .Unsubscribe() to cancel

observable := ro.Pipe2(
    ro.RangeWithInterval(0, 5, 1*time.Second),
    ro.Filter(func(x int) bool { return x%2 == 0 }),
    ro.Map(func(x int) string { return fmt.Sprintf("even-%d", x) }),
)

observable.Subscribe(ro.NewObserver(
    func(s string) { fmt.Println(s) },      // onNext
    func(err error) { log.Println(err) },    // onError
    func() { fmt.Println("Done!") },         // onComplete
))
// Output: "even-0", "even-2", "even-4", "Done!"

// Or collect synchronously:
values, err := ro.Collect(observable)

Cold vs Hot Observables

Cold (default): each .Subscribe() starts a new independent execution. Safe and predictable — use by default.

Hot: multiple subscribers share a single execution. Use when the source is expensive (WebSocket, DB poll) or subscribers must see the same events.

| Convert with | Behavior | | --- | --- | | Share() | Cold → hot with reference counting. Last unsubscribe tears down | | ShareReplay(n) | Same as Share + buffers last N values for late subscribers | | Connectable() | Cold → hot, but waits for explicit .Connect() call | | Subjects | Natively hot — call .Send(), .Error(), .Complete() directly |

| Subject | Constructor | Replay behavior | | --- | --- | --- | | PublishSubject | NewPublishSubject[T]() | None — late subscribers miss past events | | BehaviorSubject | NewBehaviorSubject[T](initial) | Replays last value to new subscribers | | ReplaySubject | NewReplaySubject[T](bufferSize) | Replays last N values | | AsyncSubject | NewAsyncSubject[T]() | Emits only last value, only on complete | | UnicastSubject | NewUnicastSubject[T](bufferSize) | Single subscriber only |

For subject details and hot observable patterns, see Subjects Guide.

Operator Quick Reference

| Category | Key operators | Purpose | | --- | --- | --- | | Creation | Just, FromSlice, FromChannel, Range, Interval, Defer, Future | Create observables from various sources | | Transform | Map, MapErr, FlatMap, Scan, Reduce, GroupBy | Transform or accumulate stream values | | Filter | Filter, Take, TakeLast, Skip, Distinct, Find, First, Last | Selectively emit values | | Combine | Merge, Concat, Zip2–Zip6, CombineLatest2–CombineLatest5, Race | Merge multiple observables | | Error | Catch, OnErrorReturn, OnErrorResumeNextWith, Retry, RetryWithConfig | Recover from errors | | Timing | Delay, DelayEach, Timeout, ThrottleTime, SampleTime, BufferWithTime | Control emission timing | | Side effect | Tap/Do, TapOnNext, TapOnError, TapOnComplete | Observe without altering stream | | Terminal | Collect, ToSlice, ToChannel, ToMap | Consume stream into Go types |

Use typed Pipe2, Pipe3 ... Pipe25 for compile-time type safety across operator chains. The untyped Pipe uses any and loses type checking.

For the complete operator catalog (150+ operators with signatures), see Operators Guide.

Common Mistakes

| Mistake | Why it fails | Fix | | --- | --- | --- | | Using ro.OnNext() without error handler | Errors are silently dropped — bugs hide in production | Use ro.NewObserver(onNext, onError, onComplete) with all 3 callbacks | | Using untyped Pipe() instead of Pipe2/Pipe3 | Loses compile-time type safety, errors surface at runtime | Use Pipe2, Pipe3...Pipe25 for typed operator chains | | Forgetting .Unsubscribe() on infinite streams | Goroutine leak — the observable runs forever | Use TakeUntil(signal), context cancellation, or explicit Unsubscribe() | | Using Share() when cold is sufficient | Unnecessary complexity, harder to reason about lifecycle | Use hot observables only when multiple consumers need the same stream | | Using samber/ro for finite slice transforms | Stream overhead (goroutines, subscriptions) for a synchronous operation | Use samber/lo — it's simpler, faster, and purpose-built for slices | | Not propagating context for cancellation | Streams ignore shutdown signals, causing resource leaks on termination | Chain ContextWithTimeout or ThrowOnContextCancel in the pipeline |

Best Practices

1. Always handle all three events — use NewObserver(onNext, onError, onComplete), not just OnNext. Unhandled errors cause silent data loss
2. Use Collect() for synchronous consumption — when the stream is finite and you need []T, Collect blocks until complete and returns the slice + error
3. Prefer typed Pipe functions — Pipe2, Pipe3...Pipe25 catch type mismatches at compile time. Reserve untyped Pipe for dynamic operator chains
4. Bound infinite streams — use Take(n), TakeUntil(signal), Timeout(d), or context cancellation. Unbounded streams leak goroutines
5. Use Tap/Do for observability — log, trace, or meter emissions without altering the stream. Chain TapOnError for error monitoring
6. Prefer samber/lo for simple transforms — if the data is a finite slice and you need Map/Filter/Reduce, use lo. Reach for ro when data arrives over time, from multiple sources, or needs retry/timeout/backpressure

Plugin Ecosystem

40+ plugins extend ro with domain-specific operators:

| Category | Plugins | Import path prefix | | --- | --- | --- | | Encoding | JSON, CSV, Base64, Gob | plugins/encoding/... | | Network | HTTP, I/O, FSNotify | plugins/http, plugins/io, plugins/fsnotify | | Scheduling | Cron, ICS | plugins/cron, plugins/ics | | Observability | Zap, Slog, Zerolog, Logrus, Sentry, Oops | plugins/observability/..., plugins/samber/oops | | Rate limiting | Native, Ulule | plugins/ratelimit/... | | Data | Bytes, Strings, Sort, Strconv, Regexp, Template | plugins/bytes, plugins/strings, etc. | | System | Process, Signal | plugins/proc, plugins/signal |

For the full plugin catalog with import paths and usage examples, see Plugin Ecosystem.

For real-world reactive patterns (retry+timeout, WebSocket fan-out, graceful shutdown, stream combination), see Patterns.

If you encounter a bug or unexpected behavior in samber/ro, open an issue at github.com/samber/ro/issues.

Cross-References

• → See golang-samber-lo skill for finite slice transforms (Map, Filter, Reduce, GroupBy) — use lo when data is already in a slice
• → See golang-samber-mo skill for monadic types (Option, Result, Either) that compose with ro pipelines
• → See golang-samber-hot skill for in-memory caching (also available as an ro plugin)
• → See golang-concurrency skill for goroutine/channel patterns when reactive streams are overkill
• → See golang-observability skill for monitoring reactive pipelines in production