github.com/cenkalti/backoff/v5 v5.0.3: Retry

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify github.com/cenkalti/backoff/v5.Retry in pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3
Demonstrate these symbols/APIs:
  - github.com/cenkalti/backoff/v5.Retry

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:3126b6033d90faf573081a50a1456e552f0106dcf8929e6cdbbc47735407c26e","contract":["Retry executes operation and returns result upon immediate success","Retry retries failed operation using configured backoff until success","Retry halts retrying immediately when operation returns Permanent error","Retry returns error after exceeding maximum attempts configured by WithMaxTries","Retry triggers notify callback with error and duration on each failed attempt","Retry respects context cancellation and aborts retrying"],"goal":"verify github.com/cenkalti/backoff/v5.Retry in pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3","kind":"HOW","packages":["pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3"],"schemaVersion":1,"symbols":["github.com/cenkalti/backoff/v5.Retry"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3"],"schemaVersion":1,"subject":"pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3","symbols":["github.com/cenkalti/backoff/v5.Retry"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require github.com/cenkalti/backoff/v5 v5.0.3

github.com/cenkalti/backoff/v5 v5.0.3 h1:ZN+IMa753KfX5hd8vVaMixjnqRZ3y8CuJKRKj1xcsSM=
github.com/cenkalti/backoff/v5 v5.0.3/go.mod h1:rkhZdG3JZukswDf7f0cwqPNk4K0sa+F97BxZthm/crw=

package main

import (
	"context"
	"fmt"

	"github.com/cenkalti/backoff/v5"
)

func main() {
	ctx := context.Background()
	attempts := 0

	result, err := backoff.Retry(ctx, func() (string, error) {
		attempts++
		if attempts < 2 {
			return "", fmt.Errorf("transient failure")
		}
		return "operation successful", nil
	}, backoff.WithBackOff(&backoff.ZeroBackOff{}), backoff.WithMaxTries(3))

	if err != nil {
		fmt.Printf("Retry failed: %v\n", err)
		return
	}

	fmt.Printf("Result: %s (after %d attempts)\n", result, attempts)
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/cenkalti/backoff/v5.Retry in pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3"
  ],
  "symbols": [
    "github.com/cenkalti/backoff/v5.Retry"
  ]
}

package main

import (
	"context"
	"errors"
	"fmt"
	"os"
	"time"

	"github.com/cenkalti/backoff/v5"
)

func main() {
	ctx := context.Background()
	b := &backoff.ZeroBackOff{}

	// 1. Retry executes operation and returns result upon immediate success
	res1, err1 := backoff.Retry(ctx, func() (string, error) {
		return "hello", nil
	}, backoff.WithBackOff(b))
	if err1 != nil || res1 != "hello" {
		fmt.Fprintf(os.Stderr, "Assertion 1 failed: res=%q, err=%v\n", res1, err1)
		os.Exit(1)
	}

	// 2. Retry retries failed operation using configured backoff until success
	attempts2 := 0
	res2, err2 := backoff.Retry(ctx, func() (int, error) {
		attempts2++
		if attempts2 < 3 {
			return 0, errors.New("temporary error")
		}
		return 42, nil
	}, backoff.WithBackOff(b))
	if err2 != nil || res2 != 42 || attempts2 != 3 {
		fmt.Fprintf(os.Stderr, "Assertion 2 failed: res=%d, err=%v, attempts=%d\n", res2, err2, attempts2)
		os.Exit(1)
	}

	// 3. Retry halts retrying immediately when operation returns Permanent error
	attempts3 := 0
	permErr := errors.New("permanent failure")
	_, err3 := backoff.Retry(ctx, func() (struct{}, error) {
		attempts3++
		return struct{}{}, backoff.Permanent(permErr)
	}, backoff.WithBackOff(b), backoff.WithMaxTries(5))
	if !errors.Is(err3, permErr) || attempts3 != 1 {
		fmt.Fprintf(os.Stderr, "Assertion 3 failed: err=%v, attempts=%d\n", err3, attempts3)
		os.Exit(1)
	}

	// 4. Retry returns error after exceeding maximum attempts configured by WithMaxTries
	attempts4 := uint(0)
	limitErr := errors.New("limit exceeded error")
	_, err4 := backoff.Retry(ctx, func() (string, error) {
		attempts4++
		return "", limitErr
	}, backoff.WithBackOff(b), backoff.WithMaxTries(3))
	if !errors.Is(err4, limitErr) || attempts4 != 3 {
		fmt.Fprintf(os.Stderr, "Assertion 4 failed: err=%v, attempts=%d\n", err4, attempts4)
		os.Exit(1)
	}

	// 5. Retry triggers notify callback with error and duration on each failed attempt
	notifyCount := 0
	_, _ = backoff.Retry(ctx, func() (int, error) {
		return 0, errors.New("callback test error")
	}, backoff.WithBackOff(b), backoff.WithMaxTries(3), backoff.WithNotify(func(err error, d time.Duration) {
		notifyCount++
	}))
	if notifyCount != 2 {
		fmt.Fprintf(os.Stderr, "Assertion 5 failed: notifyCount=%d, expected 2\n", notifyCount)
		os.Exit(1)
	}

	// 6. Retry respects context cancellation and aborts retrying
	cancelCtx, cancel := context.WithCancel(context.Background())
	cancelAttempts := 0
	_, err6 := backoff.Retry(cancelCtx, func() (string, error) {
		cancelAttempts++
		cancel()
		return "", errors.New("err before cancel")
	}, backoff.WithBackOff(b))
	if err6 == nil || cancelAttempts != 1 {
		fmt.Fprintf(os.Stderr, "Assertion 6 failed: err=%v, cancelAttempts=%d\n", err6, cancelAttempts)
		os.Exit(1)
	}

	fmt.Println("All contract assertions passed.")
}