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.

lib/api/api.go

@@ -15,7 +15,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"net"
 	"net/http"
@@ -382,7 +381,7 @@ func (s *service) Serve(ctx context.Context) error {
 		ReadTimeout: 15 * time.Second,
 		// Prevent the HTTP server from logging stuff on its own. The things we
 		// care about we log ourselves from the handlers.
-		ErrorLog: log.New(ioutil.Discard, "", 0),
+		ErrorLog: log.New(io.Discard, "", 0),
 	}
 
 	l.Infoln("GUI and API listening on", listener.Addr())
@@ -1098,7 +1097,7 @@ func (s *service) getSystemError(w http.ResponseWriter, r *http.Request) {
 }
 
 func (s *service) postSystemError(w http.ResponseWriter, r *http.Request) {
-	bs, _ := ioutil.ReadAll(r.Body)
+	bs, _ := io.ReadAll(r.Body)
 	r.Body.Close()
 	l.Warnln(string(bs))
 }
@@ -1165,7 +1164,7 @@ func (s *service) getSupportBundle(w http.ResponseWriter, r *http.Request) {
 	// Panic files
 	if panicFiles, err := filepath.Glob(filepath.Join(locations.GetBaseDir(locations.ConfigBaseDir), "panic*")); err == nil {
 		for _, f := range panicFiles {
-			if panicFile, err := ioutil.ReadFile(f); err != nil {
+			if panicFile, err := os.ReadFile(f); err != nil {
 				l.Warnf("Support bundle: failed to load %s: %s", filepath.Base(f), err)
 			} else {
 				files = append(files, fileEntry{name: filepath.Base(f), data: panicFile})
@@ -1174,7 +1173,7 @@ func (s *service) getSupportBundle(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// Archived log (default on Windows)
-	if logFile, err := ioutil.ReadFile(locations.Get(locations.LogFile)); err == nil {
+	if logFile, err := os.ReadFile(locations.Get(locations.LogFile)); err == nil {
 		files = append(files, fileEntry{name: "log-ondisk.txt", data: logFile})
 	}
 
@@ -1233,7 +1232,7 @@ func (s *service) getSupportBundle(w http.ResponseWriter, r *http.Request) {
 	zipFilePath := filepath.Join(locations.GetBaseDir(locations.ConfigBaseDir), zipFileName)
 
 	// Write buffer zip to local zip file (back up)
-	if err := ioutil.WriteFile(zipFilePath, zipFilesBuffer.Bytes(), 0600); err != nil {
+	if err := os.WriteFile(zipFilePath, zipFilesBuffer.Bytes(), 0600); err != nil {
 		l.Warnln("Support bundle: support bundle zip could not be created:", err)
 	}
 
@@ -1323,7 +1322,7 @@ func (s *service) getDBIgnores(w http.ResponseWriter, r *http.Request) {
 func (s *service) postDBIgnores(w http.ResponseWriter, r *http.Request) {
 	qs := r.URL.Query()
 
-	bs, err := ioutil.ReadAll(r.Body)
+	bs, err := io.ReadAll(r.Body)
 	r.Body.Close()
 	if err != nil {
 		http.Error(w, err.Error(), 500)
@@ -1614,7 +1613,7 @@ func (s *service) getFolderVersions(w http.ResponseWriter, r *http.Request) {
 func (s *service) postFolderVersionsRestore(w http.ResponseWriter, r *http.Request) {
 	qs := r.URL.Query()
 
-	bs, err := ioutil.ReadAll(r.Body)
+	bs, err := io.ReadAll(r.Body)
 	r.Body.Close()
 	if err != nil {
 		http.Error(w, err.Error(), 500)

lib/api/api_test.go

@@ -13,7 +13,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net"
 	"net/http"
 	"net/http/httptest"
@@ -223,7 +222,7 @@ func expectURLToContain(t *testing.T, url, exp string) {
 		return
 	}
 
-	data, err := ioutil.ReadAll(res.Body)
+	data, err := io.ReadAll(res.Body)
 	res.Body.Close()
 	if err != nil {
 		t.Error(err)
@@ -508,7 +507,7 @@ func testHTTPRequest(t *testing.T, baseURL string, tc httpTestCase, apikey strin
 		return
 	}
 
-	data, err := ioutil.ReadAll(resp.Body)
+	data, err := io.ReadAll(resp.Body)
 	if err != nil {
 		t.Errorf("Unexpected error reading %s: %v", tc.URL, err)
 		return
@@ -1137,7 +1136,7 @@ func TestBrowse(t *testing.T) {
 
 	pathSep := string(os.PathSeparator)
 
-	tmpDir, err := ioutil.TempDir("", "syncthing")
+	tmpDir, err := os.MkdirTemp("", "syncthing")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1146,7 +1145,7 @@ func TestBrowse(t *testing.T) {
 	if err := os.Mkdir(filepath.Join(tmpDir, "dir"), 0755); err != nil {
 		t.Fatal(err)
 	}
-	if err := ioutil.WriteFile(filepath.Join(tmpDir, "file"), []byte("hello"), 0644); err != nil {
+	if err := os.WriteFile(filepath.Join(tmpDir, "file"), []byte("hello"), 0644); err != nil {
 		t.Fatal(err)
 	}
 	if err := os.Mkdir(filepath.Join(tmpDir, "MiXEDCase"), 0755); err != nil {
@@ -1251,7 +1250,7 @@ func TestConfigChanges(t *testing.T) {
 			APIKey:     testAPIKey,
 		},
 	}
-	tmpFile, err := ioutil.TempFile("", "syncthing-testConfig-")
+	tmpFile, err := os.CreateTemp("", "syncthing-testConfig-")
 	if err != nil {
 		panic(err)
 	}
@@ -1393,7 +1392,7 @@ func runningInContainer() bool {
 		return false
 	}
 
-	bs, err := ioutil.ReadFile("/proc/1/cgroup")
+	bs, err := os.ReadFile("/proc/1/cgroup")
 	if err != nil {
 		return false
 	}

lib/api/auto/auto_test.go

@@ -9,7 +9,7 @@ package auto_test
 import (
 	"bytes"
 	"compress/gzip"
-	"io/ioutil"
+	"io"
 	"strings"
 	"testing"
 
@@ -28,7 +28,7 @@ func TestAssets(t *testing.T) {
 
 	var gr *gzip.Reader
 	gr, _ = gzip.NewReader(strings.NewReader(idx.Content))
-	html, _ := ioutil.ReadAll(gr)
+	html, _ := io.ReadAll(gr)
 
 	if !bytes.Contains(html, []byte("<html")) {
 		t.Fatal("No html in index.html")

lib/api/confighandler.go

@@ -9,7 +9,6 @@ package api
 import (
 	"encoding/json"
 	"io"
-	"io/ioutil"
 	"net/http"
 
 	"github.com/julienschmidt/httprouter"
@@ -407,7 +406,7 @@ func (c *configMuxBuilder) adjustLDAP(w http.ResponseWriter, r *http.Request, ld
 
 // Unmarshals the content of the given body and stores it in to (i.e. to must be a pointer).
 func unmarshalTo(body io.ReadCloser, to interface{}) error {
-	bs, err := ioutil.ReadAll(body)
+	bs, err := io.ReadAll(body)
 	body.Close()
 	if err != nil {
 		return err