net/http: fixed trivial go vet warnings

Updates #15177

Change-Id: I748f025461f313b5b426821ead695f90d3011a6b
Reviewed-on: https://go-review.googlesource.com/21677Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/net/http/client_test.go

@@ -311,7 +311,7 @@ func TestClientRedirectContext(t *testing.T) {
 	_, err := c.Do(req)
 	ue, ok := err.(*url.Error)
 	if !ok {
-		t.Fatalf("got error %T; want *url.Error")
+		t.Fatalf("got error %T; want *url.Error", err)
 	}
 	if ue.Err != ExportErrRequestCanceled && ue.Err != ExportErrRequestCanceledConn {
 		t.Errorf("url.Error.Err = %v; want errRequestCanceled or errRequestCanceledConn", ue.Err)

src/net/http/httptest/httptest_test.go

@@ -155,10 +155,10 @@ func TestNewRequest(t *testing.T) {
 		got := NewRequest(tt.method, tt.uri, tt.body)
 		slurp, err := ioutil.ReadAll(got.Body)
 		if err != nil {
-			t.Errorf("%i. ReadAll: %v", i, err)
+			t.Errorf("%d. ReadAll: %v", i, err)
 		}
 		if string(slurp) != tt.wantBody {
-			t.Errorf("%i. Body = %q; want %q", i, slurp, tt.wantBody)
+			t.Errorf("%d. Body = %q; want %q", i, slurp, tt.wantBody)
 		}
 		got.Body = nil // before DeepEqual
 		if !reflect.DeepEqual(got.URL, tt.want.URL) {