rate.Limiter — Token-Bucket Rate Limiting

// go get golang.org/x/time/rate
package main

import (
    "context"
    "fmt"
    "time"

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

func main() {
    // 5 events per second, burst up to 10
    limiter := rate.NewLimiter(5, 10)

    ctx := context.Background()
    for i := 0; i < 30; i++ {
        // Block until a token is available (or context cancels)
        if err := limiter.Wait(ctx); err != nil {
            fmt.Println("wait failed:", err); return
        }
        fmt.Printf("%2d: %s\n", i, time.Now().Format("15:04:05.000"))
    }

    // Non-blocking — Allow() returns false if a token isn't available
    if limiter.Allow() {
        // process
    }
}