Add rate limiter

pkg/http/rate_limiter.go

@@ -0,0 +1,17 @@
+package http
+
+import "time"
+
+type RateLimiter struct {
+	ticker *time.Ticker
+}
+
+func NewRateLimiter(apiRateLimitPerSecond int) *RateLimiter {
+	return &RateLimiter{
+		ticker: time.NewTicker(time.Second / time.Duration(apiRateLimitPerSecond)),
+	}
+}
+
+func (r *RateLimiter) Wait() {
+	<-r.ticker.C
+}