all: Remove usage of deprecated io/ioutil (#7971)

As of Go 1.16 io/ioutil is deprecated. This replaces usage with the
corresponding functions in package os and package io.

cmd/syncthing/cli/main.go

@@ -9,7 +9,7 @@ package cli
 import (
 	"bufio"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"os"
 	"strings"
 
@@ -151,7 +151,7 @@ func parseFlags(c *preCli) error {
 		}
 	}
 	// We don't want kong to print anything nor os.Exit (e.g. on -h)
-	parser, err := kong.New(c, kong.Writers(ioutil.Discard, ioutil.Discard), kong.Exit(func(int) {}))
+	parser, err := kong.New(c, kong.Writers(io.Discard, io.Discard), kong.Exit(func(int) {}))
 	if err != nil {
 		return err
 	}

cmd/syncthing/cli/utils.go

@@ -10,7 +10,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"mime"
 	"net/http"
 	"os"
@@ -23,7 +23,7 @@ import (
 )
 
 func responseToBArray(response *http.Response) ([]byte, error) {
-	bytes, err := ioutil.ReadAll(response.Body)
+	bytes, err := io.ReadAll(response.Body)
 	if err != nil {
 		return nil, err
 	}

cmd/syncthing/crash_reporting.go

@@ -10,7 +10,6 @@ import (
 	"bytes"
 	"context"
 	"fmt"
-	"io/ioutil"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -62,7 +61,7 @@ func uploadPanicLogs(ctx context.Context, urlBase, dir string) {
 // the log contents. A HEAD request is made to see if the log has already
 // been reported. If not, a PUT is made with the log contents.
 func uploadPanicLog(ctx context.Context, urlBase, file string) error {
-	data, err := ioutil.ReadFile(file)
+	data, err := os.ReadFile(file)
 	if err != nil {
 		return err
 	}

cmd/syncthing/decrypt/decrypt.go

@@ -12,8 +12,8 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
+	"os"
 	"path/filepath"
 
 	"github.com/syncthing/syncthing/lib/config"
@@ -112,7 +112,7 @@ func (c *CLI) withContinue(err error) error {
 // error.
 func (c *CLI) getFolderID() (string, error) {
 	tokenPath := filepath.Join(c.Path, c.TokenPath)
-	bs, err := ioutil.ReadFile(tokenPath)
+	bs, err := os.ReadFile(tokenPath)
 	if err != nil {
 		return "", fmt.Errorf("reading folder token: %w", err)
 	}

cmd/syncthing/main.go

@@ -12,7 +12,6 @@ import (
 	"crypto/tls"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"net/http"
 	_ "net/http/pprof" // Need to import this to support STPROFILER.
@@ -500,7 +499,7 @@ func upgradeViaRest() error {
 		return err
 	}
 	if resp.StatusCode != 200 {
-		bs, err := ioutil.ReadAll(resp.Body)
+		bs, err := io.ReadAll(resp.Body)
 		defer resp.Body.Close()
 		if err != nil {
 			return err

cmd/syncthing/monitor_test.go

@@ -8,7 +8,6 @@ package main
 
 import (
 	"io"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"testing"
@@ -18,7 +17,7 @@ import (
 func TestRotatedFile(t *testing.T) {
 	// Verify that log rotation happens.
 
-	dir, err := ioutil.TempDir("", "syncthing")
+	dir, err := os.MkdirTemp("", "syncthing")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -179,7 +178,7 @@ func TestAutoClosedFile(t *testing.T) {
 	}
 
 	// The file should have both writes in it.
-	bs, err := ioutil.ReadFile(file)
+	bs, err := os.ReadFile(file)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -199,7 +198,7 @@ func TestAutoClosedFile(t *testing.T) {
 	}
 
 	// It should now contain three writes, as the file is always opened for appending
-	bs, err = ioutil.ReadFile(file)
+	bs, err = os.ReadFile(file)
 	if err != nil {
 		t.Fatal(err)
 	}