racer: use select to syncrho

racer/racer.go

@@ -7,13 +7,13 @@ import (
 )
 
 func Racer(a, b string) string {
-	aDuration := measureResponseTime(a)
-	bDuration := measureResponseTime(b)
-
-	if aDuration < bDuration {
+	select {
+	// wait until channel closed
+	case <-ping(a):
 		return a
+	case <-ping(b):
+		return b
 	}
-	return b
 }
 
 func measureResponseTime(url string) time.Duration {
@@ -23,3 +23,13 @@ func measureResponseTime(url string) time.Duration {
 	fmt.Println(duration)
 	return duration
 }
+
+func ping(url string) chan struct{} {
+	ch := make(chan struct{})
+	go func() {
+		http.Get(url)
+		// if got, close channel
+		close(ch)
+	}()
+	return ch
+}