diff --git a/concurrency/concurrency.go b/concurrency/concurrency.go
new file mode 100644
index 0000000..c5a89b3
--- /dev/null
+++ b/concurrency/concurrency.go
@@ -0,0 +1,12 @@
+package concurrency
+
+type WebsiteChecker func(string) bool
+
+func CheckWebsites(wc WebsiteChecker, urls []string) map[string]bool {
+	results := make(map[string]bool)
+
+	for _, url := range urls {
+		results[url] = wc(url)
+	}
+	return results
+}
diff --git a/concurrency/concurrency_test.go b/concurrency/concurrency_test.go
new file mode 100644
index 0000000..5b2be51
--- /dev/null
+++ b/concurrency/concurrency_test.go
@@ -0,0 +1,47 @@
+package concurrency
+
+import (
+	"reflect"
+	"testing"
+	"time"
+)
+
+func mockWebsiteChecker(url string) bool {
+	return url != "waat://furhurterwe.geds"
+}
+
+func TestCheckWebsites(t *testing.T) {
+	websites := []string{
+		"http://google.com",
+		"http://blog.abc.com",
+		"waat://furhurterwe.geds",
+	}
+
+	want := map[string]bool{
+		"http://google.com":       true,
+		"http://blog.abc.com":     true,
+		"waat://furhurterwe.geds": false,
+	}
+
+	got := CheckWebsites(mockWebsiteChecker, websites)
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("wanted %v, got %v", want, got)
+	}
+}
+
+func slowStubWebsiteChecker(_ string) bool {
+	time.Sleep(20 * time.Millisecond)
+	return true
+}
+
+func BenchmarkCheckWebsites(b *testing.B) {
+	urls := make([]string, 100)
+	for i := 0; i < len(urls); i++ {
+		urls[i] = "a url"
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		CheckWebsites(slowStubWebsiteChecker, urls)
+	}
+}