racer

learn_go_with_tests/my_select/go.mod

@@ -0,0 +1,3 @@
+module my_select
+
+go 1.22.5

learn_go_with_tests/my_select/racer.go

@@ -0,0 +1,23 @@
+package my_select
+
+import (
+	"net/http"
+	"time"
+)
+
+func Racer(a string, b string) (winner string) {
+	aDuration := measureResponseTime(a)
+	bDuration := measureResponseTime(b)
+
+	if aDuration < bDuration {
+		return a
+	}
+
+	return b
+}
+
+func measureResponseTime(url string) time.Duration {
+	start := time.Now()
+	http.Get(url)
+	return time.Since(start)
+}

learn_go_with_tests/my_select/racer_test.go

@@ -0,0 +1,34 @@
+package my_select
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+)
+
+func TestRacer(t *testing.T) {
+
+	slowServer := makeDelayedServer(20 * time.Microsecond)
+	defer slowServer.Close()
+
+	fastServer := makeDelayedServer(0 * time.Microsecond)
+	defer fastServer.Close()
+
+	slowUrl := slowServer.URL
+	fastUrl := fastServer.URL
+
+	want := fastUrl
+	got := Racer(slowUrl, fastUrl)
+
+	if got != want {
+		t.Errorf("got %q, want %q", got, want)
+	}
+}
+
+func makeDelayedServer(delay time.Duration) *httptest.Server {
+	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		time.Sleep(delay)
+		w.WriteHeader(http.StatusOK)
+	}))
+}