Resonate Basic Ephemeral World Usage Go

Resonate Basic Ephemeral World Usage — Go

Version note. The Go SDK's first tagged release is 0.1.0. The tag is 0.1.0, not v0.1.0, so go get …@latest does not resolve to it (it walks main instead and returns a newer pseudo-version). Pin the tag explicitly — see Install below. APIs may still change before a 1.0. Every code block here is verified against the 0.1.0 tag source and the resonatehq-examples/*-go repos.

Overview

The ephemeral world is wherever your Go program starts: main(), an HTTP handler, a CLI entry point, a background goroutine. You use a *resonate.Resonate instance to register durable functions and invoke them top-level. Once an invocation starts, it crosses into the durable world and Resonate guarantees its completion — retries on failure, resumes after crashes, continues across process restarts.

This skill covers the Client API surface only. The Durable World (Context APIs inside workflow functions) is covered in resonate-basic-durable-world-usage-go.

Install

go get github.com/resonatehq/resonate-sdk-go@0.1.0

The tag on GitHub is 0.1.0 (no v prefix), so this is not the same as go get …@latest — @latest walks main past the tag and resolves to a newer pseudo-version instead. Requesting the tag by name resolves correctly: the module proxy mints the pseudo-version pinned to that exact commit (verify with curl -s https://proxy.golang.org/github.com/resonatehq/resonate-sdk-go/@v/0.1.0.info). Pin a later commit the same way (@<short-sha>) for reproducible builds ahead of the next tag.

Core imports:

import (
    resonate "github.com/resonatehq/resonate-sdk-go"
    "github.com/resonatehq/resonate-sdk-go/localnet"  // zero-dependency dev
    "github.com/resonatehq/resonate-sdk-go/httpnet"   // named worker groups
)

Basic Shape

A complete one-file program: register, run, read, stop.

package main

import (
    "context"
    "fmt"
    "log"
    "time"

    resonate "github.com/resonatehq/resonate-sdk-go"
)

type GreetArgs struct {
    Name string `json:"name"`
}

func greet(_ *resonate.Context, args GreetArgs) (string, error) {
    return fmt.Sprintf("hello, %s!", args.Name), nil
}

func main() {
    r, err := resonate.New(resonate.Config{URL: "http://localhost:8001"})
    if err != nil {
        log.Fatalf("resonate.New: %v", err)
    }
    defer func() { _ = r.Stop() }()

    greetFn, err := resonate.Register(r, "greet", greet)
    if err != nil {
        log.Fatalf("Register: %v", err)
    }

    ctx := context.Background()
    id := fmt.Sprintf("hello-%d", time.Now().UnixNano())

    h, err := greetFn.Run(ctx, id, GreetArgs{Name: "world"})
    if err != nil {
        log.Fatalf("Run: %v", err)
    }

    out, err := h.Result(ctx)
    if err != nil {
        log.Fatalf("Result: %v", err)
    }
    fmt.Println(out) // hello, world!
}

Initialization

Remote server

r, err := resonate.New(resonate.Config{URL: "http://localhost:8001"})

Config fields:

Network precedence: Config.URL → Config.Network → RESONATE_URL env var → resonate.ErrNetworkRequired. The only env var the constructor reads is RESONATE_URL.

Zero-dependency development (localnet)

pid := "dev-worker"
r, err := resonate.New(resonate.Config{
    Network:   localnet.NewLocal("default", &pid),
    Heartbeat: resonate.NoopHeartbeat{}, // required — localnet has no lease endpoint
})

Named worker group

There is no Group field on Config. Pass the transport explicitly:

r, err := resonate.New(resonate.Config{
    Network: httpnet.NewHTTP("http://localhost:8001", httpnet.HTTPOptions{
        Group: "worker-group-a",
    }),
})

Authentication

r, err := resonate.New(resonate.Config{
    URL:   "https://resonate.example.com",
    Token: os.Getenv("RESONATE_TOKEN"),
})

resonate.Register

Register is a package-level generic function (Go has no method-level generics). It takes the instance, a name, and the function; returns a typed *RegisteredFunc[A, R] and an error.

greetFn, err := resonate.Register(r, "greet", greet)
if err != nil {
    log.Fatalf("Register: %v", err)
}

Registered functions must have the canonical signature func(*resonate.Context, A) (R, error). Use struct{} for A or R when the function takes no input or produces no meaningful result.

RegisteredFunc.Run

Invokes a registered function in the same process and returns a typed *TypedHandle[R]. The returned handle is durable — the function will complete even if the process crashes and another worker picks it up.

h, err := greetFn.Run(ctx, "greet-1", GreetArgs{Name: "world"})
if err != nil {
    log.Fatalf("Run: %v", err)
}

result, err := h.Result(ctx) // returns (string, error) — typed
if err != nil {
    log.Fatalf("Result: %v", err)
}

RunOptions

Pass as a trailing argument to Run:

h, err := greetFn.Run(ctx, "greet-1", GreetArgs{Name: "world"}, resonate.RunOptions{
    Timeout:     60 * time.Second,
    Target:      "poll://any@workers",
    Tags:        map[string]string{"team": "checkout"},
    RetryPolicy: resonate.ConstantRetry{MaxAttempts: 3, Delay: time.Second},
})

Resonate.RPC

Invokes a registered function in a remote process by name. Returns an untyped *Handle; the target function does not need to be registered locally.

h, err := r.RPC(ctx, "greet-1", "greet", GreetArgs{Name: "world"})
if err != nil {
    log.Fatalf("RPC: %v", err)
}

var result string
if err := h.Result(ctx, &result); err != nil {
    log.Fatalf("Result: %v", err)
}

RPC accepts an optional resonate.RPCOptions{Timeout, Target, Tags, Version} as a trailing argument.

Resonate.Get

Gets a handle to an existing execution by promise ID. Returns *resonate.ServerError with Code: 404 when the promise does not exist.

h, err := r.Get(ctx, "greet-1")
if err != nil {
    log.Fatalf("Get: %v", err)
}

var result string
if err := h.Result(ctx, &result); err != nil {
    log.Fatalf("Result: %v", err)
}

Reading Handle Results

• Typed handle — RegisteredFunc.Run returns *TypedHandle[R]; call h.Result(ctx) to get (R, error) directly.
• Untyped handle — RPC and Get return *Handle; call h.Result(ctx, &out) and pass a pointer to the target variable.
• Generic helper for untyped handles:

result, err := resonate.ResultOf[string](ctx, h)

A rejected promise surfaces as *resonate.ApplicationError (or the deserialized concrete error where available).

Direct promise & schedule API

0.1.0 shipped two sub-clients on *Resonate for working with durable promises and cron schedules outside the workflow machinery — no registered function, no dispatch tags, just a promise or a schedule you manage directly. Get them via r.Promises() / r.Schedules() (methods, not fields).

r.Promises() — create, get, resolve/reject/cancel

ctx := context.Background()

// Create a promise settled by some external party (a webhook, an operator).
rec, err := r.Promises().Create(ctx, "order-1", 24*time.Hour, resonate.PromiseCreateOptions{
    Param: Order{Item: "book"},
    Tags:  map[string]string{"kind": "order"},
})
if err != nil {
    log.Fatalf("Create: %v", err)
}

// Settle it from anywhere holding the ID.
rec, err = r.Promises().Resolve(ctx, "order-1", Receipt{Total: 42})
// ...or r.Promises().Reject(ctx, "order-1", err) / r.Promises().Cancel(ctx, "order-1", nil)

// Read it back; Value decodes directly into a Go value.
rec, err = r.Promises().Get(ctx, "order-1")
var receipt Receipt
err = rec.Value.Decode(&receipt)

Resolve/Reject/Cancel handle the JSON → codec encoding for you (the same Codec the workflow machinery uses) — this is the fix for the old "manual base64 encoding" trap on the low-level Sender().PromiseSettle path (see resonate-human-in-the-loop-pattern-go and resonate-basic-debugging-go for that path, still useful for cross-process/non-Go settlement). Create's timeout is relative to now; <= 0 defaults to resonate.DefaultTopLevelTimeout (24h). Get returns *resonate.ServerError{Code: 404} when the promise does not exist.

r.Schedules() — create, get, delete

// A cron schedule creates a fresh promise on every firing, from a promise ID
// template (may include placeholders like {{.timestamp}}).
s, err := r.Schedules().Create(ctx, "nightly", "0 0 * * *", "report-{{.timestamp}}", time.Hour,
    resonate.ScheduleCreateOptions{PromiseParam: ReportArgs{Region: "us"}})
if err != nil {
    log.Fatalf("Create: %v", err)
}

s, err = r.Schedules().Get(ctx, "nightly")
err = r.Schedules().Delete(ctx, "nightly")

This creates the cron-fired promise directly — it is the Go equivalent of Python's resonate.schedules.create(...) sub-client, not the higher-level resonate.schedule(id, cron, fn, args) convenience wrapper that Python, TypeScript, and Rust also expose (which dispatches a registered function on the cron and wires the resonate:target/resonate:origin tags for you). Go's 0.1.0 tag does not have that convenience wrapper yet — to fire a registered function on a schedule, set PromiseTags: map[string]string{"resonate:target": <group>} and shape PromiseParam as map[string]any{"func": "your-fn-name", "args": args} by hand, matching what RegisteredFunc.Run and Resonate.RPC build internally.

Stop Semantics

defer func() { _ = r.Stop() }()

Stop closes the network connection, stops the heartbeat loop, and cancels the background subscription-refresh goroutine. It is idempotent.

Call Stop from processes that should exit after their work finishes: demo binaries, one-shot jobs, CI tasks, examples. Without it, background goroutines keep the process alive after main would otherwise return.

Do not call Stop on a long-running worker. Calling it tears down the channels a worker uses to receive and hold work:

• The connection to the Resonate Server closes — the worker stops receiving dispatched tasks.
• The heartbeat loop stops — the server-side TTL on in-flight tasks expires, and the server reassigns them.
• The subscription-refresh goroutine is cancelled — listeners on awaited promises are no longer re-registered.

The worker process keeps running but silently stops processing. Let SIGINT / SIGTERM end a worker's lifecycle instead.

Distinct Go Idioms

• if err != nil everywhere — both resonate.New, resonate.Register, Run, RPC, Get, and Result return errors. Use explicit checks; no method chaining.
• Option structs, not builders — RunOptions, RPCOptions, RunOpts, RPCOpts are plain structs with exported fields. Pass them as trailing arguments; zero values mean "use the default."
• Package-level generic resonate.Register — Go has no method-level generics, so registration is a free function, not a method on the instance. This is why greetFn carries the type parameters, not r.
• Exported struct fields with json tags for args — args are JSON-serialized into the durable promise so any worker that resumes the function can decode them. Unexported fields are silently dropped.
• context.Context is ctx passed to Run/RPC/Get/Result — this is the standard context.Context (cancellation, deadlines), not the *resonate.Context inside a workflow.
• defer func() { _ = r.Stop() }() — the closure-wrapped defer is idiomatic Go for deferred calls where you want to discard the error without a naked _ assignment at the call site.
• time.Duration for timeouts — 60 * time.Second, not raw integers. Durations are native time.Duration throughout the SDK.

Avoid

• Calling resonate.New with neither URL nor Network and without RESONATE_URL set — returns ErrNetworkRequired at startup.
• Using localnet without Heartbeat: resonate.NoopHeartbeat{} — the default AsyncHeartbeat issues HTTP keep-alive requests that localnet cannot serve; the heartbeat loop errors.
• Passing a Group on Config — there is no Group field. Use httpnet.NewHTTP(..., httpnet.HTTPOptions{Group: "..."}) via Config.Network.
• Using Client APIs (r.RPC, greetFn.Run) inside a durable function — those belong to the Ephemeral World. Use ctx.RPC and ctx.Run inside workflows.
• Calling Stop on a long-running worker (see Stop Semantics above).
• Relying on Config.Version in RunOptions / RPCOptions — the field is declared but not yet consumed.

Related Skills

• resonate-basic-durable-world-usage-go — Context APIs: ctx.Run, ctx.RPC, ctx.Sleep, ctx.Promise, ctx.Detached, fan-out patterns, retry policies, context accessors
• resonate-human-in-the-loop-pattern-go — Promises().Resolve/Reject/Cancel in the human-in-the-loop context, plus the CLI and low-level fallback paths
• resonate-durable-sleep-scheduled-work-go — Schedules() in the recurring-work context, and the workaround for dispatching a registered function on a cron
• durable-execution — foundational concepts; read this first if new to Resonate
• resonate-defaults — SDK-wide defaults reference (TTL, retry policy, top-level timeout, child timeout)
• resonate-basic-ephemeral-world-usage-typescript — TypeScript sibling for comparison
• resonate-basic-ephemeral-world-usage-rust — Rust sibling for comparison