golang.org/x/time v0.15.0: rate.Every

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 rate.Every in pkg:golang/golang.org/x/time@v0.15.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/time@v0.15.0
Demonstrate these symbols/APIs:
  - rate.Every

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:d16c4e4b6caae41e4278f5e5a186d408bf23d658496d5ab18eb9f68a84bbad97","contract":["rate.Every(100 * time.Millisecond) returns Limit(10.0)","rate.Every(1 * time.Second) returns Limit(1.0)","rate.Every(500 * time.Millisecond) returns Limit(2.0)","rate.Every(0) returns rate.Inf","rate.Every(-5 * time.Second) returns rate.Inf","rate.NewLimiter(rate.Every(200 * time.Millisecond), 3) creates limiter with Limit(5.0) and Burst(3)","limiter.SetLimit(rate.Every(50 * time.Millisecond)) updates limit to Limit(20.0)"],"goal":"verify rate.Every in pkg:golang/golang.org/x/time@v0.15.0","kind":"HOW","packages":["pkg:golang/golang.org/x/time@v0.15.0"],"schemaVersion":1,"symbols":["rate.Every"]},"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/golang.org/x/time@v0.15.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/time@v0.15.0","symbols":["rate.Every"],"verifierAdapter":"golang@1"}

module example.com/rate-every-sample

go 1.25.0

require golang.org/x/time v0.15.0

golang.org/x/time v0.15.0 h1:bbrp8t3bGUeFOx08pvsMYRTCVSMk89u4tKbNOZbp88U=
golang.org/x/time v0.15.0/go.mod h1:Y4YMaQmXwGQZoFaVFk4YpCt4FLQMYKZe9oeV/f4MSno=

package rateexample

import (
	"time"

	"golang.org/x/time/rate"
)

// IntervalToLimit converts a minimum duration interval between events to a rate.Limit.
func IntervalToLimit(interval time.Duration) rate.Limit {
	return rate.Every(interval)
}

// NewIntervalLimiter creates a new rate.Limiter configured with a per-interval rate and burst size.
func NewIntervalLimiter(interval time.Duration, burst int) *rate.Limiter {
	return rate.NewLimiter(rate.Every(interval), burst)
}

{
  "schemaVersion": 1,
  "goal": "verify rate.Every in pkg:golang/golang.org/x/time@v0.15.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/time@v0.15.0"
  ],
  "symbols": [
    "rate.Every"
  ]
}

package main

import (
	"fmt"
	"math"
	"os"
	"time"

	"golang.org/x/time/rate"

	rateexample "example.com/rate-every-sample"
)

func main() {
	if err := runContractTests(); err != nil {
		fmt.Fprintf(os.Stderr, "Contract test failed: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("All contract assertions passed.")
}

func runContractTests() error {
	// Assertion 1: Positive intervals convert to reciprocal frequency (events per second)
	// 100ms interval => 10 events/second
	l100ms := rateexample.IntervalToLimit(100 * time.Millisecond)
	if math.Abs(float64(l100ms)-10.0) > 1e-6 {
		return fmt.Errorf("expected 10.0 limit for 100ms, got %v", l100ms)
	}

	// Assertion 2: 1 second interval => 1 event/second
	l1s := rate.Every(1 * time.Second)
	if math.Abs(float64(l1s)-1.0) > 1e-6 {
		return fmt.Errorf("expected 1.0 limit for 1s, got %v", l1s)
	}

	// Assertion 3: 500ms interval => 2 events/second
	l500ms := rate.Every(500 * time.Millisecond)
	if math.Abs(float64(l500ms)-2.0) > 1e-6 {
		return fmt.Errorf("expected 2.0 limit for 500ms, got %v", l500ms)
	}

	// Assertion 4: 0 duration returns rate.Inf (infinite rate, no limit)
	l0 := rate.Every(0)
	if l0 != rate.Inf {
		return fmt.Errorf("expected rate.Inf for 0 duration, got %v", l0)
	}

	// Assertion 5: Negative duration returns rate.Inf
	lNeg := rate.Every(-5 * time.Second)
	if lNeg != rate.Inf {
		return fmt.Errorf("expected rate.Inf for negative duration, got %v", lNeg)
	}

	// Assertion 6: rate.NewLimiter with rate.Every sets the expected Limit and Burst
	limiter := rateexample.NewIntervalLimiter(200*time.Millisecond, 3)
	if limiter.Limit() != rate.Limit(5.0) {
		return fmt.Errorf("expected limiter limit 5.0, got %v", limiter.Limit())
	}
	if limiter.Burst() != 3 {
		return fmt.Errorf("expected limiter burst 3, got %d", limiter.Burst())
	}

	// Assertion 7: Dynamic limit updates with rate.Every
	limiter.SetLimit(rate.Every(50 * time.Millisecond))
	if math.Abs(float64(limiter.Limit())-20.0) > 1e-6 {
		return fmt.Errorf("expected updated limit 20.0, got %v", limiter.Limit())
	}

	return nil
}