attack: Measure latency when requests timeout (tsenart#404)

Fixes tsenart#402

lib/attack.go

@@ -285,18 +285,19 @@ func (a *Attacker) hit(tr Targeter, name string) *Result {
 		err error
 	)
 
-	defer func() {
-		if err != nil {
-			res.Error = err.Error()
-		}
-	}()
-
 	a.seqmu.Lock()
 	res.Timestamp = a.began.Add(time.Since(a.began))
 	res.Seq = a.seq
 	a.seq++
 	a.seqmu.Unlock()
 
+	defer func() {
+		res.Latency = time.Since(res.Timestamp)
+		if err != nil {
+			res.Error = err.Error()
+		}
+	}()
+
 	if err = tr(&tgt); err != nil {
 		a.Stop()
 		return &res
@@ -324,7 +325,6 @@ func (a *Attacker) hit(tr Targeter, name string) *Result {
 		return &res
 	}
 
-	res.Latency = time.Since(res.Timestamp)
 	res.BytesIn = uint64(len(res.Body))
 
 	if req.ContentLength != -1 {

lib/attack_test.go

@@ -117,10 +117,15 @@ func TestTimeout(t *testing.T) {
 	atk := NewAttacker(Timeout(10 * time.Millisecond))
 	tr := NewStaticTargeter(Target{Method: "GET", URL: server.URL})
 	res := atk.hit(tr, "")
+
 	want := "Client.Timeout exceeded while awaiting headers"
 	if got := res.Error; !strings.Contains(got, want) {
 		t.Fatalf("want: '%v' in '%v'", want, got)
 	}
+
+	if res.Latency == 0 {
+		t.Fatal("Latency wasn't captured with a timed-out result")
+	}
 }
 
 func TestLocalAddr(t *testing.T) {