diff --git a/dns/dnsmessage/message.go b/dns/dnsmessage/message.go
index a656efc128..64df432ba5 100644
--- a/dns/dnsmessage/message.go
+++ b/dns/dnsmessage/message.go
@@ -197,7 +197,7 @@ const hexDigits = "0123456789abcdef"
 
 func printString(str []byte) string {
 	buf := make([]byte, 0, len(str))
-	for i := 0; i < len(str); i++ {
+	for i := range len(str) {
 		c := str[i]
 		if c == '.' || c == '-' || c == ' ' ||
 			'A' <= c && c <= 'Z' ||
diff --git a/dns/dnsmessage/message_test.go b/dns/dnsmessage/message_test.go
index 1fa93e63ad..00891a457a 100644
--- a/dns/dnsmessage/message_test.go
+++ b/dns/dnsmessage/message_test.go
@@ -1279,7 +1279,7 @@ func BenchmarkParsing(b *testing.B) {
 	}
 
 	b.ReportAllocs()
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		benchmarkParsing(b, buf)
 	}
 }
@@ -1422,7 +1422,7 @@ func BenchmarkPack(b *testing.B) {
 
 	b.ReportAllocs()
 
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		if _, err := msg.Pack(); err != nil {
 			b.Fatal("Message.Pack() =", err)
 		}
@@ -1435,7 +1435,7 @@ func BenchmarkAppendPack(b *testing.B) {
 
 	b.ReportAllocs()
 
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		if _, err := msg.AppendPack(buf[:0]); err != nil {
 			b.Fatal("Message.AppendPack() = ", err)
 		}
diff --git a/http/httpguts/httplex.go b/http/httpguts/httplex.go
index 9b4de94019..092cc0cb2d 100644
--- a/http/httpguts/httplex.go
+++ b/http/httpguts/httplex.go
@@ -197,7 +197,7 @@ func ValidHeaderFieldName(v string) bool {
 	if len(v) == 0 {
 		return false
 	}
-	for i := 0; i < len(v); i++ {
+	for i := range len(v) {
 		if !isTokenTable[v[i]] {
 			return false
 		}
@@ -218,7 +218,7 @@ func ValidHostHeader(h string) bool {
 	// But we're going to be much more lenient for now and just
 	// search for any byte that's not a valid byte in any of those
 	// expressions.
-	for i := 0; i < len(h); i++ {
+	for i := range len(h) {
 		if !validHostByte[h[i]] {
 			return false
 		}
@@ -301,7 +301,7 @@ var validHostByte = [256]bool{
 // This function does not (yet?) properly handle the rejection of
 // strings that begin or end with SP or HTAB.
 func ValidHeaderFieldValue(v string) bool {
-	for i := 0; i < len(v); i++ {
+	for i := range len(v) {
 		b := v[i]
 		if isCTL(b) && !isLWS(b) {
 			return false
@@ -311,7 +311,7 @@ func ValidHeaderFieldValue(v string) bool {
 }
 
 func isASCII(s string) bool {
-	for i := 0; i < len(s); i++ {
+	for i := range len(s) {
 		if s[i] >= utf8.RuneSelf {
 			return false
 		}
diff --git a/http/httpguts/httplex_test.go b/http/httpguts/httplex_test.go
index 791440b1a7..dee81d3da4 100644
--- a/http/httpguts/httplex_test.go
+++ b/http/httpguts/httplex_test.go
@@ -31,7 +31,7 @@ func TestIsTokenRune(t *testing.T) {
 }
 
 func BenchmarkIsTokenRune(b *testing.B) {
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		var r rune
 		for ; r < 1024; r++ {
 			IsTokenRune(r)
@@ -140,7 +140,7 @@ func BenchmarkValidHeaderFieldName(b *testing.B) {
 	}
 	b.ReportAllocs()
 	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		for _, name := range names {
 			ValidHeaderFieldName(name)
 		}
diff --git a/http/httpproxy/proxy.go b/http/httpproxy/proxy.go
index d89c257ae7..3cb855a894 100644
--- a/http/httpproxy/proxy.go
+++ b/http/httpproxy/proxy.go
@@ -313,7 +313,7 @@ func idnaASCII(v string) (string, error) {
 }
 
 func isASCII(s string) bool {
-	for i := 0; i < len(s); i++ {
+	for i := range len(s) {
 		if s[i] >= utf8.RuneSelf {
 			return false
 		}
diff --git a/http/httpproxy/proxy_test.go b/http/httpproxy/proxy_test.go
index a1dd2e83fd..06a5be4c10 100644
--- a/http/httpproxy/proxy_test.go
+++ b/http/httpproxy/proxy_test.go
@@ -394,7 +394,7 @@ func BenchmarkProxyForURL(b *testing.B) {
 		}
 		proxyFunc := cfg.ProxyFunc()
 		b.Run(test.host, func(b *testing.B) {
-			for n := 0; n < b.N; n++ {
+			for range b.N {
 				if au, e := proxyFunc(u); e != nil && test.match == (au != nil) {
 					b.Errorf("useProxy(%v) = %v, want %v", test.host, !test.match, test.match)
 				}
diff --git a/http2/ascii.go b/http2/ascii.go
index 17caa20586..05483db7ee 100644
--- a/http2/ascii.go
+++ b/http2/ascii.go
@@ -16,7 +16,7 @@ func asciiEqualFold(s, t string) bool {
 	if len(s) != len(t) {
 		return false
 	}
-	for i := 0; i < len(s); i++ {
+	for i := range len(s) {
 		if lower(s[i]) != lower(t[i]) {
 			return false
 		}
@@ -35,7 +35,7 @@ func lower(b byte) byte {
 // isASCIIPrint returns whether s is ASCII and printable according to
 // https://tools.ietf.org/html/rfc20#section-4.2.
 func isASCIIPrint(s string) bool {
-	for i := 0; i < len(s); i++ {
+	for i := range len(s) {
 		if s[i] < ' ' || s[i] > '~' {
 			return false
 		}
diff --git a/http2/frame.go b/http2/frame.go
index e6f728c261..2aff1ae21f 100644
--- a/http2/frame.go
+++ b/http2/frame.go
@@ -771,7 +771,7 @@ func (f *SettingsFrame) IsAck() bool {
 
 func (f *SettingsFrame) Value(id SettingID) (v uint32, ok bool) {
 	f.checkValid()
-	for i := 0; i < f.NumSettings(); i++ {
+	for i := range f.NumSettings() {
 		if s := f.Setting(i); s.ID == id {
 			return s.Val, true
 		}
@@ -800,7 +800,7 @@ func (f *SettingsFrame) HasDuplicates() bool {
 	// If it's small enough (the common case), just do the n^2
 	// thing and avoid a map allocation.
 	if num < 10 {
-		for i := 0; i < num; i++ {
+		for i := range num {
 			idi := f.Setting(i).ID
 			for j := i + 1; j < num; j++ {
 				idj := f.Setting(j).ID
@@ -812,7 +812,7 @@ func (f *SettingsFrame) HasDuplicates() bool {
 		return false
 	}
 	seen := map[SettingID]bool{}
-	for i := 0; i < num; i++ {
+	for i := range num {
 		id := f.Setting(i).ID
 		if seen[id] {
 			return true
@@ -826,7 +826,7 @@ func (f *SettingsFrame) HasDuplicates() bool {
 // It stops and returns the first error.
 func (f *SettingsFrame) ForeachSetting(fn func(Setting) error) error {
 	f.checkValid()
-	for i := 0; i < f.NumSettings(); i++ {
+	for i := range f.NumSettings() {
 		if err := fn(f.Setting(i)); err != nil {
 			return err
 		}
diff --git a/http2/frame_test.go b/http2/frame_test.go
index 68505317e1..1a8c2e541b 100644
--- a/http2/frame_test.go
+++ b/http2/frame_test.go
@@ -985,7 +985,7 @@ func TestMetaFrameHeader(t *testing.T) {
 			w: func(f *Framer) {
 				var he hpackEncoder
 				var pairs = []string{":method", "GET", ":path", "/"}
-				for i := 0; i < 100; i++ {
+				for range 100 {
 					pairs = append(pairs, "foo", "bar")
 				}
 				all := he.encodeHeaderRaw(t, pairs...)
@@ -1129,21 +1129,21 @@ func TestSetReuseFrames(t *testing.T) {
 	// SetReuseFrames only currently implements reuse of DataFrames.
 	firstDf := readAndVerifyDataFrame("ABC", 3, fr, buf, t)
 
-	for i := 0; i < 10; i++ {
+	for range 10 {
 		df := readAndVerifyDataFrame("XYZ", 3, fr, buf, t)
 		if df != firstDf {
 			t.Errorf("Expected Framer to return references to the same DataFrame. Have %v and %v", &df, &firstDf)
 		}
 	}
 
-	for i := 0; i < 10; i++ {
+	for range 10 {
 		df := readAndVerifyDataFrame("", 0, fr, buf, t)
 		if df != firstDf {
 			t.Errorf("Expected Framer to return references to the same DataFrame. Have %v and %v", &df, &firstDf)
 		}
 	}
 
-	for i := 0; i < 10; i++ {
+	for range 10 {
 		df := readAndVerifyDataFrame("HHH", 3, fr, buf, t)
 		if df != firstDf {
 			t.Errorf("Expected Framer to return references to the same DataFrame. Have %v and %v", &df, &firstDf)
@@ -1158,7 +1158,7 @@ func TestSetReuseFramesMoreThanOnce(t *testing.T) {
 	firstDf := readAndVerifyDataFrame("ABC", 3, fr, buf, t)
 	fr.SetReuseFrames()
 
-	for i := 0; i < 10; i++ {
+	for range 10 {
 		df := readAndVerifyDataFrame("XYZ", 3, fr, buf, t)
 		// SetReuseFrames should be idempotent
 		fr.SetReuseFrames()
diff --git a/http2/gotrack.go b/http2/gotrack.go
index 9933c9f8c7..bd4f591306 100644
--- a/http2/gotrack.go
+++ b/http2/gotrack.go
@@ -116,7 +116,7 @@ func parseUintBytes(s []byte, base int, bitSize int) (n uint64, err error) {
 	cutoff = cutoff64(base)
 	maxVal = 1<<uint(bitSize) - 1
 
-	for i := 0; i < len(s); i++ {
+	for i := range len(s) {
 		var v byte
 		d := s[i]
 		switch {
diff --git a/http2/server_push_test.go b/http2/server_push_test.go
index 69e4c3b12d..9213dd65ce 100644
--- a/http2/server_push_test.go
+++ b/http2/server_push_test.go
@@ -110,7 +110,7 @@ func TestServer_Push_Success(t *testing.T) {
 	// Send one request, which should push two responses.
 	st.greet()
 	getSlash(st)
-	for k := 0; k < 3; k++ {
+	for k := range 3 {
 		select {
 		case <-time.After(2 * time.Second):
 			t.Errorf("timeout waiting for handler %d to finish", k)
@@ -274,7 +274,7 @@ func TestServer_Push_SuccessNoRace(t *testing.T) {
 	// Send one request, which should push one response.
 	st.greet()
 	getSlash(st)
-	for k := 0; k < 2; k++ {
+	for k := range 2 {
 		select {
 		case <-time.After(2 * time.Second):
 			t.Errorf("timeout waiting for handler %d to finish", k)
@@ -542,7 +542,7 @@ func TestServer_Push_Underflow(t *testing.T) {
 	// Send several requests.
 	st.greet()
 	const numRequests = 4
-	for i := 0; i < numRequests; i++ {
+	for i := range numRequests {
 		st.writeHeaders(HeadersFrameParam{
 			StreamID:      uint32(1 + i*2), // clients send odd numbers
 			BlockFragment: st.encodeHeader(),
diff --git a/http2/server_test.go b/http2/server_test.go
index b27a127a5e..099ee8fcef 100644
--- a/http2/server_test.go
+++ b/http2/server_test.go
@@ -447,7 +447,7 @@ func (st *serverTester) greetAndCheckSettings(checkSetting func(s Setting) error
 	var gotSettingsAck bool
 	var gotWindowUpdate bool
 
-	for i := 0; i < 2; i++ {
+	for range 2 {
 		f := st.readFrame()
 		if f == nil {
 			st.t.Fatal("wanted a settings ACK and window update, got none")
@@ -1197,7 +1197,7 @@ func TestServer_MaxQueuedControlFrames(t *testing.T) {
 	// Send maxQueuedControlFrames pings, plus a few extra
 	// to account for ones that enter the server's write buffer.
 	const extraPings = 2
-	for i := 0; i < maxQueuedControlFrames+extraPings; i++ {
+	for range maxQueuedControlFrames + extraPings {
 		pingData := [8]byte{1, 2, 3, 4, 5, 6, 7, 8}
 		st.fr.WritePing(false, pingData)
 	}
@@ -1209,7 +1209,7 @@ func TestServer_MaxQueuedControlFrames(t *testing.T) {
 
 	st.advance(goAwayTimeout)
 	// Some frames may have persisted in the server's buffers.
-	for i := 0; i < 10; i++ {
+	for range 10 {
 		if st.readFrame() == nil {
 			break
 		}
@@ -1406,7 +1406,7 @@ func TestServer_RSTStream_Unblocks_Header_Write(t *testing.T) {
 	if testing.Short() {
 		n = 5
 	}
-	for i := 0; i < n; i++ {
+	for range n {
 		testServer_RSTStream_Unblocks_Header_Write(t)
 	}
 }
@@ -2282,12 +2282,12 @@ func TestServer_Rejects_Too_Many_Streams(t *testing.T) {
 			EndHeaders:    true,
 		})
 	}
-	for i := 0; i < defaultMaxStreams; i++ {
+	for range defaultMaxStreams {
 		sendReq(streamID())
 		<-inHandler
 	}
 	defer func() {
-		for i := 0; i < defaultMaxStreams; i++ {
+		for range defaultMaxStreams {
 			leaveHandler <- true
 		}
 	}()
@@ -2330,7 +2330,7 @@ func TestServer_Rejects_Too_Many_Streams(t *testing.T) {
 func TestServer_Response_ManyHeaders_With_Continuation(t *testing.T) {
 	testServerResponse(t, func(w http.ResponseWriter, r *http.Request) error {
 		h := w.Header()
-		for i := 0; i < 5000; i++ {
+		for i := range 5000 {
 			h.Set(fmt.Sprintf("x-header-%d", i), fmt.Sprintf("x-value-%d", i))
 		}
 		return nil
@@ -2912,7 +2912,7 @@ func BenchmarkServerGets(b *testing.B) {
 		b.Fatal(err)
 	}
 
-	for i := 0; i < b.N; i++ {
+	for i := range b.N {
 		id := 1 + uint32(i)*2
 		st.writeHeaders(HeadersFrameParam{
 			StreamID:      id,
@@ -2949,7 +2949,7 @@ func BenchmarkServerPosts(b *testing.B) {
 		b.Fatal(err)
 	}
 
-	for i := 0; i < b.N; i++ {
+	for i := range b.N {
 		id := 1 + uint32(i)*2
 		st.writeHeaders(HeadersFrameParam{
 			StreamID:      id,
@@ -3295,7 +3295,7 @@ func BenchmarkServer_GetRequest(b *testing.B) {
 		b.Fatal(err)
 	}
 	hbf := st.encodeHeader(":method", "GET")
-	for i := 0; i < b.N; i++ {
+	for i := range b.N {
 		streamID := uint32(1 + 2*i)
 		st.writeHeaders(HeadersFrameParam{
 			StreamID:      streamID,
@@ -3326,7 +3326,7 @@ func BenchmarkServer_PostRequest(b *testing.B) {
 		b.Fatal(err)
 	}
 	hbf := st.encodeHeader(":method", "POST")
-	for i := 0; i < b.N; i++ {
+	for i := range b.N {
 		streamID := uint32(1 + 2*i)
 		st.writeHeaders(HeadersFrameParam{
 			StreamID:      streamID,
@@ -3598,7 +3598,7 @@ func TestUnreadFlowControlReturned_Server(t *testing.T) {
 			if testing.Short() {
 				iters = 20
 			}
-			for i := 0; i < iters; i++ {
+			for range iters {
 				body := io.MultiReader(
 					io.LimitReader(neverEnding('A'), 16<<10),
 					funcReader(func([]byte) (n int, err error) {
@@ -3703,7 +3703,7 @@ func TestServerIdleTimeout_AfterRequest(t *testing.T) {
 // Verify that it doesn't race.
 // See https://github.com/grpc/grpc-go/pull/938
 func TestRequestBodyReadCloseRace(t *testing.T) {
-	for i := 0; i < 100; i++ {
+	for range 100 {
 		body := &requestBody{
 			pipe: &pipe{
 				b: new(bytes.Buffer),
@@ -3733,7 +3733,7 @@ func TestIssue20704Race(t *testing.T) {
 	)
 
 	ts := newTestServer(t, func(w http.ResponseWriter, r *http.Request) {
-		for i := 0; i < itemCount; i++ {
+		for range itemCount {
 			_, err := w.Write(make([]byte, itemSize))
 			if err != nil {
 				return
@@ -3745,7 +3745,7 @@ func TestIssue20704Race(t *testing.T) {
 	defer tr.CloseIdleConnections()
 	cl := &http.Client{Transport: tr}
 
-	for i := 0; i < 1000; i++ {
+	for range 1000 {
 		resp, err := cl.Get(ts.URL)
 		if err != nil {
 			t.Fatal(err)
@@ -4474,7 +4474,7 @@ func TestServerMaxHandlerGoroutines(t *testing.T) {
 	streamID += 2
 
 	// Start another two requests. Don't reset these.
-	for i := 0; i < 2; i++ {
+	for range 2 {
 		st.writeHeaders(HeadersFrameParam{
 			StreamID:      streamID,
 			BlockFragment: st.encodeHeader(),
@@ -4537,7 +4537,7 @@ func TestServerContinuationFlood(t *testing.T) {
 		BlockFragment: st.encodeHeader(),
 		EndStream:     true,
 	})
-	for i := 0; i < 1000; i++ {
+	for i := range 1000 {
 		st.fr.WriteContinuation(1, false, st.encodeHeaderRaw(
 			fmt.Sprintf("x-%v", i), "1234567890",
 		))
@@ -4697,7 +4697,7 @@ func TestServerWriteByteTimeout(t *testing.T) {
 	})
 
 	// Read a few bytes, staying just under WriteByteTimeout.
-	for i := 0; i < 10; i++ {
+	for i := range 10 {
 		st.advance(timeout - 1)
 		if n, err := st.cc.Read(make([]byte, 1)); n != 1 || err != nil {
 			t.Fatalf("read %v: %v, %v; want 1, nil", i, n, err)
diff --git a/http2/transport_test.go b/http2/transport_test.go
index 596499f3ea..06e0d32aef 100644
--- a/http2/transport_test.go
+++ b/http2/transport_test.go
@@ -127,7 +127,7 @@ func TestIdleConnTimeout(t *testing.T) {
 				tr.IdleConnTimeout = test.idleConnTimeout
 			})
 			var tc *testClientConn
-			for i := 0; i < 3; i++ {
+			for i := range 3 {
 				req, _ := http.NewRequest("GET", "https://dummy.tld/", nil)
 				rt := tt.roundTrip(req)
 
@@ -411,7 +411,7 @@ func testTransportGetGotConnHooks(t *testing.T, useClient bool) {
 		getConns int32
 		gotConns int32
 	)
-	for i := 0; i < 2; i++ {
+	for i := range 2 {
 		trace := &httptrace.ClientTrace{
 			GetConn: func(hostport string) {
 				atomic.AddInt32(&getConns, 1)
@@ -4509,10 +4509,6 @@ func newCloseChecker(r io.ReadCloser) *closeChecker {
 	return &closeChecker{r, make(chan struct{})}
 }
 
-func newStaticCloseChecker(body string) *closeChecker {
-	return newCloseChecker(io.NopCloser(strings.NewReader("body")))
-}
-
 func (rc *closeChecker) Read(b []byte) (n int, err error) {
 	select {
 	default: