Go rate limiter 
This package provides a Golang implementation of the leaky-bucket rate limit algorithm. This implementation refills the bucket based on the time elapsed between requests instead of requiring an interval clock to fill the bucket discretely.
Create a rate limiter with a maximum number of operations to perform per second. Call Take() before each operation. Take will sleep until you can continue.
import (
"fmt"
"time"
"go.uber.org/ratelimit"
)
func main() {
rl := ratelimit.New(100) // per second
prev := time.Now()
for i := 0; i < 10; i++ {
now := rl.Take()
fmt.Println(i, now.Sub(prev))
prev = now
}
// Output:
// 0 0
// 1 10ms
// 2 10ms
// 3 10ms
// 4 10ms
// 5 10ms
// 6 10ms
// 7 10ms
// 8 10ms
// 9 10ms
}