Implementing Rate Limiting in Go APIs.

RateLimiter.go

package main

import (
	"fmt"
	"sync"
	"time"
)

type RateLimiter struct {
	sync.Mutex
	requests      int
	requestsLimit int
	interval      time.Duration
}

func NewRateLimiter(requestsLimit int, interval time.Duration) *RateLimiter {
	return &RateLimiter{
		requests:      0,
		requestsLimit: requestsLimit,
		interval:      interval,
	}
}

func (rl *RateLimiter) AllowRequest() bool {
	rl.Lock()
	defer rl.Unlock()

	if rl.requests >= rl.requestsLimit {
		return false
	}

	rl.requests++
	time.AfterFunc(rl.interval, func() {
		rl.Lock()
		defer rl.Unlock()
		rl.requests--
	})
	return true
}

func main() {
	rl := NewRateLimiter(3, time.Second*10)

	for i := 1; i <= 10; i++ {
		if rl.AllowRequest() {
			fmt.Printf("Request %d allowed.\n", i)
		} else {
			fmt.Printf("Request %d denied.\n", i)
		}
		time.Sleep(time.Second)
	}
}