diff --git a/lessons/215/go-app/main.go b/lessons/215/go-app/main.go
index ea3bdcca9..0ba48a746 100644
--- a/lessons/215/go-app/main.go
+++ b/lessons/215/go-app/main.go
@@ -50,5 +50,5 @@ func (ms *MyServer) getHealth(w http.ResponseWriter, req *http.Request) {
 func (ms *MyServer) getDevices(w http.ResponseWriter, req *http.Request) {
 	device := Device{Id: 1, Mac: "EF-2B-C4-F5-D6-34", Firmware: "2.1.5"}
 
-	renderJSON(w, &device, 200)
+	renderJSON(w, device, 200)
 }
diff --git a/lessons/215/go-app/main_bench_test.go b/lessons/215/go-app/main_bench_test.go
new file mode 100644
index 000000000..20521c135
--- /dev/null
+++ b/lessons/215/go-app/main_bench_test.go
@@ -0,0 +1,27 @@
+package main
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func BenchmarkGetDevicesParallel(b *testing.B) {
+	ms := &MyServer{}
+	b.ReportAllocs()
+
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			req := httptest.NewRequest("GET", "/api/devices", nil)
+			rec := httptest.NewRecorder()
+
+			ms.getDevices(rec, req)
+
+			res := rec.Result()
+			if res.StatusCode != http.StatusOK {
+				b.Fatalf("expected status %d, got %d", http.StatusOK, res.StatusCode)
+			}
+			res.Body.Close()
+		}
+	})
+}