all: update references to symbols moved from io/ioutil to io

The old ioutil references are still valid, but update our code
to reflect best practices and get used to the new locations.

Code compiled with the bootstrap toolchain
(cmd/asm, cmd/dist, cmd/compile, debug/elf)
must remain Go 1.4-compatible and is excluded.
Also excluded vendored code.

For #41190.

Change-Id: I6d86f2bf7bc37a9d904b6cee3fe0c7af6d94d5b1
Reviewed-on: https://go-review.googlesource.com/c/go/+/263142
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

4 files changed, 35 insertions, 38 deletions

diff --git a/src/net/http/httputil/dump.go b/src/net/http/httputil/dump.go
index c97be066d7..4c9d28bed8 100644
--- a/src/net/http/httputil/dump.go
+++ b/src/net/http/httputil/dump.go
@@ -10,7 +10,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net"
 	"net/http"
 	"net/url"
@@ -35,7 +34,7 @@ func drainBody(b io.ReadCloser) (r1, r2 io.ReadCloser, err error) {
 	if err = b.Close(); err != nil {
 		return nil, b, err
 	}
-	return ioutil.NopCloser(&buf), ioutil.NopCloser(bytes.NewReader(buf.Bytes())), nil
+	return io.NopCloser(&buf), io.NopCloser(bytes.NewReader(buf.Bytes())), nil
 }
 
 // dumpConn is a net.Conn which writes to Writer and reads from Reader
@@ -81,7 +80,7 @@ func DumpRequestOut(req *http.Request, body bool) ([]byte, error) {
 	if !body {
 		contentLength := outgoingLength(req)
 		if contentLength != 0 {
-			req.Body = ioutil.NopCloser(io.LimitReader(neverEnding('x'), contentLength))
+			req.Body = io.NopCloser(io.LimitReader(neverEnding('x'), contentLength))
 			dummyBody = true
 		}
 	} else {
@@ -133,7 +132,7 @@ func DumpRequestOut(req *http.Request, body bool) ([]byte, error) {
 		if err == nil {
 			// Ensure all the body is read; otherwise
 			// we'll get a partial dump.
-			io.Copy(ioutil.Discard, req.Body)
+			io.Copy(io.Discard, req.Body)
 			req.Body.Close()
 		}
 		select {
@@ -296,7 +295,7 @@ func (failureToReadBody) Read([]byte) (int, error) { return 0, errNoBody }
 func (failureToReadBody) Close() error             { return nil }
 
 // emptyBody is an instance of empty reader.
-var emptyBody = ioutil.NopCloser(strings.NewReader(""))
+var emptyBody = io.NopCloser(strings.NewReader(""))
 
 // DumpResponse is like DumpRequest but dumps a response.
 func DumpResponse(resp *http.Response, body bool) ([]byte, error) {
diff --git a/src/net/http/httputil/dump_test.go b/src/net/http/httputil/dump_test.go
index ead56bc172..7571eb0820 100644
--- a/src/net/http/httputil/dump_test.go
+++ b/src/net/http/httputil/dump_test.go
@@ -9,7 +9,6 @@ import (
 	"bytes"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/http"
 	"net/url"
 	"runtime"
@@ -268,7 +267,7 @@ func TestDumpRequest(t *testing.T) {
 			}
 			switch b := ti.Body.(type) {
 			case []byte:
-				req.Body = ioutil.NopCloser(bytes.NewReader(b))
+				req.Body = io.NopCloser(bytes.NewReader(b))
 			case func() io.ReadCloser:
 				req.Body = b()
 			default:
@@ -363,7 +362,7 @@ var dumpResTests = []struct {
 			Header: http.Header{
 				"Foo": []string{"Bar"},
 			},
-			Body: ioutil.NopCloser(strings.NewReader("foo")), // shouldn't be used
+			Body: io.NopCloser(strings.NewReader("foo")), // shouldn't be used
 		},
 		body: false, // to verify we see 50, not empty or 3.
 		want: `HTTP/1.1 200 OK
@@ -379,7 +378,7 @@ Foo: Bar`,
 			ProtoMajor:    1,
 			ProtoMinor:    1,
 			ContentLength: 3,
-			Body:          ioutil.NopCloser(strings.NewReader("foo")),
+			Body:          io.NopCloser(strings.NewReader("foo")),
 		},
 		body: true,
 		want: `HTTP/1.1 200 OK
@@ -396,7 +395,7 @@ foo`,
 			ProtoMajor:       1,
 			ProtoMinor:       1,
 			ContentLength:    -1,
-			Body:             ioutil.NopCloser(strings.NewReader("foo")),
+			Body:             io.NopCloser(strings.NewReader("foo")),
 			TransferEncoding: []string{"chunked"},
 		},
 		body: true,
diff --git a/src/net/http/httputil/example_test.go b/src/net/http/httputil/example_test.go
index 6191603674..b77a243ca3 100644
--- a/src/net/http/httputil/example_test.go
+++ b/src/net/http/httputil/example_test.go
@@ -6,7 +6,7 @@ package httputil_test
 
 import (
 	"fmt"
-	"io/ioutil"
+	"io"
 	"log"
 	"net/http"
 	"net/http/httptest"
@@ -39,7 +39,7 @@ func ExampleDumpRequest() {
 	}
 	defer resp.Body.Close()
 
-	b, err := ioutil.ReadAll(resp.Body)
+	b, err := io.ReadAll(resp.Body)
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -111,7 +111,7 @@ func ExampleReverseProxy() {
 		log.Fatal(err)
 	}
 
-	b, err := ioutil.ReadAll(resp.Body)
+	b, err := io.ReadAll(resp.Body)
 	if err != nil {
 		log.Fatal(err)
 	}
diff --git a/src/net/http/httputil/reverseproxy_test.go b/src/net/http/httputil/reverseproxy_test.go
index cc05d55d87..3acbd940e4 100644
--- a/src/net/http/httputil/reverseproxy_test.go
+++ b/src/net/http/httputil/reverseproxy_test.go
@@ -13,7 +13,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"net/http"
 	"net/http/httptest"
@@ -84,7 +83,7 @@ func TestReverseProxy(t *testing.T) {
 		t.Fatal(err)
 	}
 	proxyHandler := NewSingleHostReverseProxy(backendURL)
-	proxyHandler.ErrorLog = log.New(ioutil.Discard, "", 0) // quiet for tests
+	proxyHandler.ErrorLog = log.New(io.Discard, "", 0) // quiet for tests
 	frontend := httptest.NewServer(proxyHandler)
 	defer frontend.Close()
 	frontendClient := frontend.Client()
@@ -124,7 +123,7 @@ func TestReverseProxy(t *testing.T) {
 	if cookie := res.Cookies()[0]; cookie.Name != "flavor" {
 		t.Errorf("unexpected cookie %q", cookie.Name)
 	}
-	bodyBytes, _ := ioutil.ReadAll(res.Body)
+	bodyBytes, _ := io.ReadAll(res.Body)
 	if g, e := string(bodyBytes), backendResponse; g != e {
 		t.Errorf("got body %q; expected %q", g, e)
 	}
@@ -218,7 +217,7 @@ func TestReverseProxyStripHeadersPresentInConnection(t *testing.T) {
 		t.Fatalf("Get: %v", err)
 	}
 	defer res.Body.Close()
-	bodyBytes, err := ioutil.ReadAll(res.Body)
+	bodyBytes, err := io.ReadAll(res.Body)
 	if err != nil {
 		t.Fatalf("reading body: %v", err)
 	}
@@ -271,7 +270,7 @@ func TestXForwardedFor(t *testing.T) {
 	if g, e := res.StatusCode, backendStatus; g != e {
 		t.Errorf("got res.StatusCode %d; expected %d", g, e)
 	}
-	bodyBytes, _ := ioutil.ReadAll(res.Body)
+	bodyBytes, _ := io.ReadAll(res.Body)
 	if g, e := string(bodyBytes), backendResponse; g != e {
 		t.Errorf("got body %q; expected %q", g, e)
 	}
@@ -373,7 +372,7 @@ func TestReverseProxyFlushInterval(t *testing.T) {
 		t.Fatalf("Get: %v", err)
 	}
 	defer res.Body.Close()
-	if bodyBytes, _ := ioutil.ReadAll(res.Body); string(bodyBytes) != expected {
+	if bodyBytes, _ := io.ReadAll(res.Body); string(bodyBytes) != expected {
 		t.Errorf("got body %q; expected %q", bodyBytes, expected)
 	}
 }
@@ -441,7 +440,7 @@ func TestReverseProxyCancellation(t *testing.T) {
 
 	defer backend.Close()
 
-	backend.Config.ErrorLog = log.New(ioutil.Discard, "", 0)
+	backend.Config.ErrorLog = log.New(io.Discard, "", 0)
 
 	backendURL, err := url.Parse(backend.URL)
 	if err != nil {
@@ -452,7 +451,7 @@ func TestReverseProxyCancellation(t *testing.T) {
 
 	// Discards errors of the form:
 	// http: proxy error: read tcp 127.0.0.1:44643: use of closed network connection
-	proxyHandler.ErrorLog = log.New(ioutil.Discard, "", 0)
+	proxyHandler.ErrorLog = log.New(io.Discard, "", 0)
 
 	frontend := httptest.NewServer(proxyHandler)
 	defer frontend.Close()
@@ -504,7 +503,7 @@ func TestNilBody(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer res.Body.Close()
-	slurp, err := ioutil.ReadAll(res.Body)
+	slurp, err := io.ReadAll(res.Body)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -533,7 +532,7 @@ func TestUserAgentHeader(t *testing.T) {
 		t.Fatal(err)
 	}
 	proxyHandler := NewSingleHostReverseProxy(backendURL)
-	proxyHandler.ErrorLog = log.New(ioutil.Discard, "", 0) // quiet for tests
+	proxyHandler.ErrorLog = log.New(io.Discard, "", 0) // quiet for tests
 	frontend := httptest.NewServer(proxyHandler)
 	defer frontend.Close()
 	frontendClient := frontend.Client()
@@ -606,7 +605,7 @@ func TestReverseProxyGetPutBuffer(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Get: %v", err)
 	}
-	slurp, err := ioutil.ReadAll(res.Body)
+	slurp, err := io.ReadAll(res.Body)
 	res.Body.Close()
 	if err != nil {
 		t.Fatalf("reading body: %v", err)
@@ -627,7 +626,7 @@ func TestReverseProxy_Post(t *testing.T) {
 	const backendStatus = 200
 	var requestBody = bytes.Repeat([]byte("a"), 1<<20)
 	backend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		slurp, err := ioutil.ReadAll(r.Body)
+		slurp, err := io.ReadAll(r.Body)
 		if err != nil {
 			t.Errorf("Backend body read = %v", err)
 		}
@@ -656,7 +655,7 @@ func TestReverseProxy_Post(t *testing.T) {
 	if g, e := res.StatusCode, backendStatus; g != e {
 		t.Errorf("got res.StatusCode %d; expected %d", g, e)
 	}
-	bodyBytes, _ := ioutil.ReadAll(res.Body)
+	bodyBytes, _ := io.ReadAll(res.Body)
 	if g, e := string(bodyBytes), backendResponse; g != e {
 		t.Errorf("got body %q; expected %q", g, e)
 	}
@@ -672,7 +671,7 @@ func (fn RoundTripperFunc) RoundTrip(req *http.Request) (*http.Response, error)
 func TestReverseProxy_NilBody(t *testing.T) {
 	backendURL, _ := url.Parse("http://fake.tld/")
 	proxyHandler := NewSingleHostReverseProxy(backendURL)
-	proxyHandler.ErrorLog = log.New(ioutil.Discard, "", 0) // quiet for tests
+	proxyHandler.ErrorLog = log.New(io.Discard, "", 0) // quiet for tests
 	proxyHandler.Transport = RoundTripperFunc(func(req *http.Request) (*http.Response, error) {
 		if req.Body != nil {
 			t.Error("Body != nil; want a nil Body")
@@ -695,8 +694,8 @@ func TestReverseProxy_NilBody(t *testing.T) {
 // Issue 33142: always allocate the request headers
 func TestReverseProxy_AllocatedHeader(t *testing.T) {
 	proxyHandler := new(ReverseProxy)
-	proxyHandler.ErrorLog = log.New(ioutil.Discard, "", 0) // quiet for tests
-	proxyHandler.Director = func(*http.Request) {}         // noop
+	proxyHandler.ErrorLog = log.New(io.Discard, "", 0) // quiet for tests
+	proxyHandler.Director = func(*http.Request) {}     // noop
 	proxyHandler.Transport = RoundTripperFunc(func(req *http.Request) (*http.Response, error) {
 		if req.Header == nil {
 			t.Error("Header == nil; want a non-nil Header")
@@ -722,7 +721,7 @@ func TestReverseProxyModifyResponse(t *testing.T) {
 
 	rpURL, _ := url.Parse(backendServer.URL)
 	rproxy := NewSingleHostReverseProxy(rpURL)
-	rproxy.ErrorLog = log.New(ioutil.Discard, "", 0) // quiet for tests
+	rproxy.ErrorLog = log.New(io.Discard, "", 0) // quiet for tests
 	rproxy.ModifyResponse = func(resp *http.Response) error {
 		if resp.Header.Get("X-Hit-Mod") != "true" {
 			return fmt.Errorf("tried to by-pass proxy")
@@ -821,7 +820,7 @@ func TestReverseProxyErrorHandler(t *testing.T) {
 			if rproxy.Transport == nil {
 				rproxy.Transport = failingRoundTripper{}
 			}
-			rproxy.ErrorLog = log.New(ioutil.Discard, "", 0) // quiet for tests
+			rproxy.ErrorLog = log.New(io.Discard, "", 0) // quiet for tests
 			if tt.errorHandler != nil {
 				rproxy.ErrorHandler = tt.errorHandler
 			}
@@ -896,7 +895,7 @@ func (t *staticTransport) RoundTrip(r *http.Request) (*http.Response, error) {
 func BenchmarkServeHTTP(b *testing.B) {
 	res := &http.Response{
 		StatusCode: 200,
-		Body:       ioutil.NopCloser(strings.NewReader("")),
+		Body:       io.NopCloser(strings.NewReader("")),
 	}
 	proxy := &ReverseProxy{
 		Director:  func(*http.Request) {},
@@ -953,7 +952,7 @@ func TestServeHTTPDeepCopy(t *testing.T) {
 // Issue 18327: verify we always do a deep copy of the Request.Header map
 // before any mutations.
 func TestClonesRequestHeaders(t *testing.T) {
-	log.SetOutput(ioutil.Discard)
+	log.SetOutput(io.Discard)
 	defer log.SetOutput(os.Stderr)
 	req, _ := http.NewRequest("GET", "http://foo.tld/", nil)
 	req.RemoteAddr = "1.2.3.4:56789"
@@ -1031,7 +1030,7 @@ func (cc *checkCloser) Read(b []byte) (int, error) {
 
 // Issue 23643: panic on body copy error
 func TestReverseProxy_PanicBodyError(t *testing.T) {
-	log.SetOutput(ioutil.Discard)
+	log.SetOutput(io.Discard)
 	defer log.SetOutput(os.Stderr)
 	backendServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		out := "this call was relayed by the reverse proxy"
@@ -1148,7 +1147,7 @@ func TestReverseProxyWebSocket(t *testing.T) {
 
 	backURL, _ := url.Parse(backendServer.URL)
 	rproxy := NewSingleHostReverseProxy(backURL)
-	rproxy.ErrorLog = log.New(ioutil.Discard, "", 0) // quiet for tests
+	rproxy.ErrorLog = log.New(io.Discard, "", 0) // quiet for tests
 	rproxy.ModifyResponse = func(res *http.Response) error {
 		res.Header.Add("X-Modified", "true")
 		return nil
@@ -1265,7 +1264,7 @@ func TestReverseProxyWebSocketCancelation(t *testing.T) {
 
 	backendURL, _ := url.Parse(cst.URL)
 	rproxy := NewSingleHostReverseProxy(backendURL)
-	rproxy.ErrorLog = log.New(ioutil.Discard, "", 0) // quiet for tests
+	rproxy.ErrorLog = log.New(io.Discard, "", 0) // quiet for tests
 	rproxy.ModifyResponse = func(res *http.Response) error {
 		res.Header.Add("X-Modified", "true")
 		return nil
@@ -1352,7 +1351,7 @@ func TestUnannouncedTrailer(t *testing.T) {
 		t.Fatal(err)
 	}
 	proxyHandler := NewSingleHostReverseProxy(backendURL)
-	proxyHandler.ErrorLog = log.New(ioutil.Discard, "", 0) // quiet for tests
+	proxyHandler.ErrorLog = log.New(io.Discard, "", 0) // quiet for tests
 	frontend := httptest.NewServer(proxyHandler)
 	defer frontend.Close()
 	frontendClient := frontend.Client()
@@ -1362,7 +1361,7 @@ func TestUnannouncedTrailer(t *testing.T) {
 		t.Fatalf("Get: %v", err)
 	}
 
-	ioutil.ReadAll(res.Body)
+	io.ReadAll(res.Body)
 
 	if g, w := res.Trailer.Get("X-Unannounced-Trailer"), "unannounced_trailer_value"; g != w {
 		t.Errorf("Trailer(X-Unannounced-Trailer) = %q; want %q", g, w)