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>

2 files changed, 9 insertions, 10 deletions

diff --git a/src/text/tabwriter/tabwriter_test.go b/src/text/tabwriter/tabwriter_test.go
index 6a97d4c427..a51358dbed 100644
--- a/src/text/tabwriter/tabwriter_test.go
+++ b/src/text/tabwriter/tabwriter_test.go
@@ -8,7 +8,6 @@ import (
 	"bytes"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"testing"
 	. "text/tabwriter"
 )
@@ -664,7 +663,7 @@ func BenchmarkTable(b *testing.B) {
 				b.Run("new", func(b *testing.B) {
 					b.ReportAllocs()
 					for i := 0; i < b.N; i++ {
-						w := NewWriter(ioutil.Discard, 4, 4, 1, ' ', 0) // no particular reason for these settings
+						w := NewWriter(io.Discard, 4, 4, 1, ' ', 0) // no particular reason for these settings
 						// Write the line h times.
 						for j := 0; j < h; j++ {
 							w.Write(line)
@@ -675,7 +674,7 @@ func BenchmarkTable(b *testing.B) {
 
 				b.Run("reuse", func(b *testing.B) {
 					b.ReportAllocs()
-					w := NewWriter(ioutil.Discard, 4, 4, 1, ' ', 0) // no particular reason for these settings
+					w := NewWriter(io.Discard, 4, 4, 1, ' ', 0) // no particular reason for these settings
 					for i := 0; i < b.N; i++ {
 						// Write the line h times.
 						for j := 0; j < h; j++ {
@@ -696,7 +695,7 @@ func BenchmarkPyramid(b *testing.B) {
 		b.Run(fmt.Sprintf("%d", x), func(b *testing.B) {
 			b.ReportAllocs()
 			for i := 0; i < b.N; i++ {
-				w := NewWriter(ioutil.Discard, 4, 4, 1, ' ', 0) // no particular reason for these settings
+				w := NewWriter(io.Discard, 4, 4, 1, ' ', 0) // no particular reason for these settings
 				// Write increasing prefixes of that line.
 				for j := 0; j < x; j++ {
 					w.Write(line[:j*2])
@@ -718,7 +717,7 @@ func BenchmarkRagged(b *testing.B) {
 		b.Run(fmt.Sprintf("%d", h), func(b *testing.B) {
 			b.ReportAllocs()
 			for i := 0; i < b.N; i++ {
-				w := NewWriter(ioutil.Discard, 4, 4, 1, ' ', 0) // no particular reason for these settings
+				w := NewWriter(io.Discard, 4, 4, 1, ' ', 0) // no particular reason for these settings
 				// Write the lines in turn h times.
 				for j := 0; j < h; j++ {
 					w.Write(lines[j%len(lines)])
@@ -746,7 +745,7 @@ lines
 func BenchmarkCode(b *testing.B) {
 	b.ReportAllocs()
 	for i := 0; i < b.N; i++ {
-		w := NewWriter(ioutil.Discard, 4, 4, 1, ' ', 0) // no particular reason for these settings
+		w := NewWriter(io.Discard, 4, 4, 1, ' ', 0) // no particular reason for these settings
 		// The code is small, so it's reasonable for the tabwriter user
 		// to write it all at once, or buffer the writes.
 		w.Write([]byte(codeSnippet))
diff --git a/src/text/template/exec_test.go b/src/text/template/exec_test.go
index 3309b33e3e..1611ee054f 100644
--- a/src/text/template/exec_test.go
+++ b/src/text/template/exec_test.go
@@ -9,7 +9,7 @@ import (
 	"errors"
 	"flag"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"reflect"
 	"strings"
 	"testing"
@@ -1328,7 +1328,7 @@ func TestExecuteGivesExecError(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	err = tmpl.Execute(ioutil.Discard, 0)
+	err = tmpl.Execute(io.Discard, 0)
 	if err == nil {
 		t.Fatal("expected error; got none")
 	}
@@ -1474,7 +1474,7 @@ func TestEvalFieldErrors(t *testing.T) {
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
 			tmpl := Must(New("tmpl").Parse(tc.src))
-			err := tmpl.Execute(ioutil.Discard, tc.value)
+			err := tmpl.Execute(io.Discard, tc.value)
 			got := "<nil>"
 			if err != nil {
 				got = err.Error()
@@ -1491,7 +1491,7 @@ func TestMaxExecDepth(t *testing.T) {
 		t.Skip("skipping in -short mode")
 	}
 	tmpl := Must(New("tmpl").Parse(`{{template "tmpl" .}}`))
-	err := tmpl.Execute(ioutil.Discard, nil)
+	err := tmpl.Execute(io.Discard, nil)
 	got := "<nil>"
 	if err != nil {
 		got = err.Error()