Move from deprecated ioutil to os and io packages (#4364)

26 files changed, 71 insertions, 84 deletions

diff --git a/.golangci.yml b/.golangci.yml
index 2c6acca5e..79fd8f2ff 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -1,6 +1,6 @@
 linters-settings:
   errcheck:
-    ignore: fmt:.*,io/ioutil:^Read.*,go.uber.org/zap/zapcore:^Add.*
+    ignore: fmt:.*,go.uber.org/zap/zapcore:^Add.*
     ignoretests: true
 
 linters:
diff --git a/admin.go b/admin.go
index fb451682e..684526dd0 100644
--- a/admin.go
+++ b/admin.go
@@ -26,7 +26,6 @@ import (
 	"expvar"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net"
 	"net/http"
 	"net/http/pprof"
@@ -1202,7 +1201,7 @@ var (
 // will get deleted before the process gracefully exits.
 func PIDFile(filename string) error {
 	pid := []byte(strconv.Itoa(os.Getpid()) + "\n")
-	err := ioutil.WriteFile(filename, pid, 0600)
+	err := os.WriteFile(filename, pid, 0600)
 	if err != nil {
 		return err
 	}
diff --git a/caddy.go b/caddy.go
index ba025b18a..a7e99c111 100644
--- a/caddy.go
+++ b/caddy.go
@@ -20,7 +20,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"net/http"
 	"os"
@@ -300,7 +299,7 @@ func unsyncedDecodeAndRun(cfgJSON []byte, allowPersist bool) error {
 				zap.String("dir", dir),
 				zap.Error(err))
 		} else {
-			err := ioutil.WriteFile(ConfigAutosavePath, cfgJSON, 0600)
+			err := os.WriteFile(ConfigAutosavePath, cfgJSON, 0600)
 			if err == nil {
 				Log().Info("autosaved config (load with --resume flag)", zap.String("file", ConfigAutosavePath))
 			} else {
@@ -700,13 +699,13 @@ func ParseDuration(s string) (time.Duration, error) {
 // have its own unique ID.
 func InstanceID() (uuid.UUID, error) {
 	uuidFilePath := filepath.Join(AppDataDir(), "instance.uuid")
-	uuidFileBytes, err := ioutil.ReadFile(uuidFilePath)
+	uuidFileBytes, err := os.ReadFile(uuidFilePath)
 	if os.IsNotExist(err) {
 		uuid, err := uuid.NewRandom()
 		if err != nil {
 			return uuid, err
 		}
-		err = ioutil.WriteFile(uuidFilePath, []byte(uuid.String()), 0600)
+		err = os.WriteFile(uuidFilePath, []byte(uuid.String()), 0600)
 		return uuid, err
 	} else if err != nil {
 		return [16]byte{}, err
diff --git a/caddyconfig/caddyfile/parse.go b/caddyconfig/caddyfile/parse.go
index 0fe07ab97..8591759bc 100755
--- a/caddyconfig/caddyfile/parse.go
+++ b/caddyconfig/caddyfile/parse.go
@@ -17,7 +17,7 @@ package caddyfile
 import (
 	"bytes"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"log"
 	"os"
 	"path/filepath"
@@ -447,7 +447,7 @@ func (p *parser) doSingleImport(importFile string) ([]Token, error) {
 		return nil, p.Errf("Could not import %s: is a directory", importFile)
 	}
 
-	input, err := ioutil.ReadAll(file)
+	input, err := io.ReadAll(file)
 	if err != nil {
 		return nil, p.Errf("Could not read imported file %s: %v", importFile, err)
 	}
diff --git a/caddyconfig/caddyfile/parse_test.go b/caddyconfig/caddyfile/parse_test.go
index 0996ed046..8d43e1aa5 100755
--- a/caddyconfig/caddyfile/parse_test.go
+++ b/caddyconfig/caddyfile/parse_test.go
@@ -16,7 +16,6 @@ package caddyfile
 
 import (
 	"bytes"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"testing"
@@ -280,7 +279,7 @@ func TestRecursiveImport(t *testing.T) {
 	}
 
 	// test relative recursive import
-	err = ioutil.WriteFile(recursiveFile1, []byte(
+	err = os.WriteFile(recursiveFile1, []byte(
 		`localhost
 		dir1
 		import recursive_import_test2`), 0644)
@@ -289,7 +288,7 @@ func TestRecursiveImport(t *testing.T) {
 	}
 	defer os.Remove(recursiveFile1)
 
-	err = ioutil.WriteFile(recursiveFile2, []byte("dir2 1"), 0644)
+	err = os.WriteFile(recursiveFile2, []byte("dir2 1"), 0644)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -314,7 +313,7 @@ func TestRecursiveImport(t *testing.T) {
 	}
 
 	// test absolute recursive import
-	err = ioutil.WriteFile(recursiveFile1, []byte(
+	err = os.WriteFile(recursiveFile1, []byte(
 		`localhost
 		dir1
 		import `+recursiveFile2), 0644)
@@ -370,7 +369,7 @@ func TestDirectiveImport(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = ioutil.WriteFile(directiveFile, []byte(`prop1 1
+	err = os.WriteFile(directiveFile, []byte(`prop1 1
 	prop2 2`), 0644)
 	if err != nil {
 		t.Fatal(err)
@@ -633,7 +632,7 @@ func TestSnippets(t *testing.T) {
 }
 
 func writeStringToTempFileOrDie(t *testing.T, str string) (pathToFile string) {
-	file, err := ioutil.TempFile("", t.Name())
+	file, err := os.CreateTemp("", t.Name())
 	if err != nil {
 		panic(err) // get a stack trace so we know where this was called from.
 	}
diff --git a/caddyconfig/httpcaddyfile/builtins.go b/caddyconfig/httpcaddyfile/builtins.go
index d52c5ef80..7fdd3e8a4 100644
--- a/caddyconfig/httpcaddyfile/builtins.go
+++ b/caddyconfig/httpcaddyfile/builtins.go
@@ -19,8 +19,8 @@ import (
 	"encoding/pem"
 	"fmt"
 	"html"
-	"io/ioutil"
 	"net/http"
+	"os"
 	"reflect"
 	"strconv"
 	"strings"
@@ -230,7 +230,7 @@ func parseTLS(h Helper) ([]ConfigValue, error) {
 							return nil, h.ArgErr()
 						}
 						filename := h.Val()
-						certDataPEM, err := ioutil.ReadFile(filename)
+						certDataPEM, err := os.ReadFile(filename)
 						if err != nil {
 							return nil, err
 						}
diff --git a/caddyconfig/httploader.go b/caddyconfig/httploader.go
index d9e222bb4..396e15369 100644
--- a/caddyconfig/httploader.go
+++ b/caddyconfig/httploader.go
@@ -18,8 +18,9 @@ import (
 	"crypto/tls"
 	"crypto/x509"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
+	"os"
 	"time"
 
 	"github.com/caddyserver/caddy/v2"
@@ -95,7 +96,7 @@ func (hl HTTPLoader) LoadConfig(ctx caddy.Context) ([]byte, error) {
 		return nil, fmt.Errorf("server responded with HTTP %d", resp.StatusCode)
 	}
 
-	body, err := ioutil.ReadAll(resp.Body)
+	body, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return nil, err
 	}
@@ -144,7 +145,7 @@ func (hl HTTPLoader) makeClient(ctx caddy.Context) (*http.Client, error) {
 		if len(hl.TLS.RootCAPEMFiles) > 0 {
 			rootPool := x509.NewCertPool()
 			for _, pemFile := range hl.TLS.RootCAPEMFiles {
-				pemData, err := ioutil.ReadFile(pemFile)
+				pemData, err := os.ReadFile(pemFile)
 				if err != nil {
 					return nil, fmt.Errorf("failed reading ca cert: %v", err)
 				}
diff --git a/caddytest/caddytest.go b/caddytest/caddytest.go
index 094e45c6d..3be332ec1 100644
--- a/caddytest/caddytest.go
+++ b/caddytest/caddytest.go
@@ -7,7 +7,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"log"
 	"net"
 	"net/http"
@@ -129,7 +129,7 @@ func (tc *Tester) initServer(rawConfig string, configType string) error {
 				return
 			}
 			defer res.Body.Close()
-			body, _ := ioutil.ReadAll(res.Body)
+			body, _ := io.ReadAll(res.Body)
 
 			var out bytes.Buffer
 			_ = json.Indent(&out, body, "", "  ")
@@ -162,7 +162,7 @@ func (tc *Tester) initServer(rawConfig string, configType string) error {
 	timeElapsed(start, "caddytest: config load time")
 
 	defer res.Body.Close()
-	body, err := ioutil.ReadAll(res.Body)
+	body, err := io.ReadAll(res.Body)
 	if err != nil {
 		tc.t.Errorf("unable to read response. %s", err)
 		return err
@@ -202,7 +202,7 @@ func (tc *Tester) ensureConfigRunning(rawConfig string, configType string) error
 			return nil
 		}
 		defer resp.Body.Close()
-		actualBytes, err := ioutil.ReadAll(resp.Body)
+		actualBytes, err := io.ReadAll(resp.Body)
 		if err != nil {
 			return nil
 		}
@@ -471,7 +471,7 @@ func (tc *Tester) AssertResponse(req *http.Request, expectedStatusCode int, expe
 	resp := tc.AssertResponseCode(req, expectedStatusCode)
 
 	defer resp.Body.Close()
-	bytes, err := ioutil.ReadAll(resp.Body)
+	bytes, err := io.ReadAll(resp.Body)
 	if err != nil {
 		tc.t.Fatalf("unable to read the response body %s", err)
 	}
diff --git a/caddytest/integration/caddyfile_adapt_test.go b/caddytest/integration/caddyfile_adapt_test.go
index e10989994..5b052df49 100644
--- a/caddytest/integration/caddyfile_adapt_test.go
+++ b/caddytest/integration/caddyfile_adapt_test.go
@@ -3,7 +3,7 @@ package integration
 import (
 	jsonMod "encoding/json"
 	"fmt"
-	"io/ioutil"
+	"os"
 	"path/filepath"
 	"regexp"
 	"strings"
@@ -14,7 +14,7 @@ import (
 
 func TestCaddyfileAdaptToJSON(t *testing.T) {
 	// load the list of test files from the dir
-	files, err := ioutil.ReadDir("./caddyfile_adapt")
+	files, err := os.ReadDir("./caddyfile_adapt")
 	if err != nil {
 		t.Errorf("failed to read caddyfile_adapt dir: %s", err)
 	}
@@ -29,7 +29,7 @@ func TestCaddyfileAdaptToJSON(t *testing.T) {
 
 		// read the test file
 		filename := f.Name()
-		data, err := ioutil.ReadFile("./caddyfile_adapt/" + filename)
+		data, err := os.ReadFile("./caddyfile_adapt/" + filename)
 		if err != nil {
 			t.Errorf("failed to read %s dir: %s", filename, err)
 		}
diff --git a/caddytest/integration/reverseproxy_test.go b/caddytest/integration/reverseproxy_test.go
index 422f67169..ca11287a7 100644
--- a/caddytest/integration/reverseproxy_test.go
+++ b/caddytest/integration/reverseproxy_test.go
@@ -2,7 +2,6 @@ package integration
 
 import (
 	"fmt"
-	"io/ioutil"
 	"net"
 	"net/http"
 	"os"
@@ -85,7 +84,7 @@ func TestDialWithPlaceholderUnix(t *testing.T) {
 		t.SkipNow()
 	}
 
-	f, err := ioutil.TempFile("", "*.sock")
+	f, err := os.CreateTemp("", "*.sock")
 	if err != nil {
 		t.Errorf("failed to create TempFile: %s", err)
 		return
@@ -387,7 +386,7 @@ func TestReverseProxyHealthCheckUnixSocket(t *testing.T) {
 		t.SkipNow()
 	}
 	tester := caddytest.NewTester(t)
-	f, err := ioutil.TempFile("", "*.sock")
+	f, err := os.CreateTemp("", "*.sock")
 	if err != nil {
 		t.Errorf("failed to create TempFile: %s", err)
 		return
@@ -442,7 +441,7 @@ func TestReverseProxyHealthCheckUnixSocketWithoutPort(t *testing.T) {
 		t.SkipNow()
 	}
 	tester := caddytest.NewTester(t)
-	f, err := ioutil.TempFile("", "*.sock")
+	f, err := os.CreateTemp("", "*.sock")
 	if err != nil {
 		t.Errorf("failed to create TempFile: %s", err)
 		return
diff --git a/caddytest/integration/stream_test.go b/caddytest/integration/stream_test.go
index b6447c68d..d5edb793e 100644
--- a/caddytest/integration/stream_test.go
+++ b/caddytest/integration/stream_test.go
@@ -6,7 +6,6 @@ import (
 	"crypto/rand"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/http"
 	"net/http/httputil"
 	"net/url"
@@ -110,7 +109,7 @@ func TestH2ToH2CStream(t *testing.T) {
 	r, w := io.Pipe()
 	req := &http.Request{
 		Method: "PUT",
-		Body:   ioutil.NopCloser(r),
+		Body:   io.NopCloser(r),
 		URL: &url.URL{
 			Scheme: "https",
 			Host:   "127.0.0.1:9443",
@@ -134,7 +133,7 @@ func TestH2ToH2CStream(t *testing.T) {
 	}()
 
 	defer resp.Body.Close()
-	bytes, err := ioutil.ReadAll(resp.Body)
+	bytes, err := io.ReadAll(resp.Body)
 	if err != nil {
 		t.Fatalf("unable to read the response body %s", err)
 	}
@@ -319,7 +318,7 @@ func TestH2ToH1ChunkedResponse(t *testing.T) {
 	r, w := io.Pipe()
 	req := &http.Request{
 		Method: "PUT",
-		Body:   ioutil.NopCloser(r),
+		Body:   io.NopCloser(r),
 		URL: &url.URL{
 			Scheme: "https",
 			Host:   "127.0.0.1:9443",
@@ -342,7 +341,7 @@ func TestH2ToH1ChunkedResponse(t *testing.T) {
 	}
 
 	defer resp.Body.Close()
-	bytes, err := ioutil.ReadAll(resp.Body)
+	bytes, err := io.ReadAll(resp.Body)
 	if err != nil {
 		t.Fatalf("unable to read the response body %s", err)
 	}
@@ -370,7 +369,7 @@ func testH2ToH1ChunkedResponseServeH1(t *testing.T) *http.Server {
 		}
 
 		defer r.Body.Close()
-		bytes, err := ioutil.ReadAll(r.Body)
+		bytes, err := io.ReadAll(r.Body)
 		if err != nil {
 			t.Fatalf("unable to read the response body %s", err)
 		}
diff --git a/cmd/commandfuncs.go b/cmd/commandfuncs.go
index 8f1c68c82..cc3f65c70 100644
--- a/cmd/commandfuncs.go
+++ b/cmd/commandfuncs.go
@@ -22,7 +22,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"net"
 	"net/http"
@@ -181,7 +180,7 @@ func cmdRun(fl Flags) (int, error) {
 	var config []byte
 	var err error
 	if runCmdResumeFlag {
-		config, err = ioutil.ReadFile(caddy.ConfigAutosavePath)
+		config, err = os.ReadFile(caddy.ConfigAutosavePath)
 		if os.IsNotExist(err) {
 			// not a bad error; just can't resume if autosave file doesn't exist
 			caddy.Log().Info("no autosave file exists", zap.String("autosave_file", caddy.ConfigAutosavePath))
@@ -219,7 +218,7 @@ func cmdRun(fl Flags) (int, error) {
 	// if we are to report to another process the successful start
 	// of the server, do so now by echoing back contents of stdin
 	if runCmdPingbackFlag != "" {
-		confirmationBytes, err := ioutil.ReadAll(os.Stdin)
+		confirmationBytes, err := io.ReadAll(os.Stdin)
 		if err != nil {
 			return caddy.ExitCodeFailedStartup,
 				fmt.Errorf("reading confirmation bytes from stdin: %v", err)
@@ -457,7 +456,7 @@ func cmdAdaptConfig(fl Flags) (int, error) {
 			fmt.Errorf("unrecognized config adapter: %s", adaptCmdAdapterFlag)
 	}
 
-	input, err := ioutil.ReadFile(adaptCmdInputFlag)
+	input, err := os.ReadFile(adaptCmdInputFlag)
 	if err != nil {
 		return caddy.ExitCodeFailedStartup,
 			fmt.Errorf("reading input file: %v", err)
@@ -541,7 +540,7 @@ func cmdFmt(fl Flags) (int, error) {
 
 	// as a special case, read from stdin if the file name is "-"
 	if formatCmdConfigFile == "-" {
-		input, err := ioutil.ReadAll(os.Stdin)
+		input, err := io.ReadAll(os.Stdin)
 		if err != nil {
 			return caddy.ExitCodeFailedStartup,
 				fmt.Errorf("reading stdin: %v", err)
@@ -550,7 +549,7 @@ func cmdFmt(fl Flags) (int, error) {
 		return caddy.ExitCodeSuccess, nil
 	}
 
-	input, err := ioutil.ReadFile(formatCmdConfigFile)
+	input, err := os.ReadFile(formatCmdConfigFile)
 	if err != nil {
 		return caddy.ExitCodeFailedStartup,
 			fmt.Errorf("reading input file: %v", err)
@@ -559,7 +558,7 @@ func cmdFmt(fl Flags) (int, error) {
 	output := caddyfile.Format(input)
 
 	if fl.Bool("overwrite") {
-		if err := ioutil.WriteFile(formatCmdConfigFile, output, 0600); err != nil {
+		if err := os.WriteFile(formatCmdConfigFile, output, 0600); err != nil {
 			return caddy.ExitCodeFailedStartup, nil
 		}
 	} else {
@@ -699,7 +698,7 @@ func apiRequest(adminAddr, method, uri string, headers http.Header, body io.Read
 
 	// if it didn't work, let the user know
 	if resp.StatusCode >= 400 {
-		respBody, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1024*10))
+		respBody, err := io.ReadAll(io.LimitReader(resp.Body, 1024*10))
 		if err != nil {
 			return fmt.Errorf("HTTP %d: reading error message: %v", resp.StatusCode, err)
 		}
diff --git a/cmd/main.go b/cmd/main.go
index 8a9a28968..7c33c55fb 100644
--- a/cmd/main.go
+++ b/cmd/main.go
@@ -20,7 +20,6 @@ import (
 	"flag"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"net"
 	"os"
@@ -94,7 +93,7 @@ func Main() {
 // the bytes in expect, or returns an error if it doesn't.
 func handlePingbackConn(conn net.Conn, expect []byte) error {
 	defer conn.Close()
-	confirmationBytes, err := ioutil.ReadAll(io.LimitReader(conn, 32))
+	confirmationBytes, err := io.ReadAll(io.LimitReader(conn, 32))
 	if err != nil {
 		return err
 	}
@@ -124,9 +123,9 @@ func loadConfig(configFile, adapterName string) ([]byte, string, error) {
 	var err error
 	if configFile != "" {
 		if configFile == "-" {
-			config, err = ioutil.ReadAll(os.Stdin)
+			config, err = io.ReadAll(os.Stdin)
 		} else {
-			config, err = ioutil.ReadFile(configFile)
+			config, err = os.ReadFile(configFile)
 		}
 		if err != nil {
 			return nil, "", fmt.Errorf("reading config file: %v", err)
@@ -140,7 +139,7 @@ func loadConfig(configFile, adapterName string) ([]byte, string, error) {
 		// plugged in, and if so, try using a default Caddyfile
 		cfgAdapter = caddyconfig.GetAdapter("caddyfile")
 		if cfgAdapter != nil {
-			config, err = ioutil.ReadFile("Caddyfile")
+			config, err = os.ReadFile("Caddyfile")
 			if os.IsNotExist(err) {
 				// okay, no default Caddyfile; pretend like this never happened
 				cfgAdapter = nil
diff --git a/logging.go b/logging.go
index 7837145da..129aec430 100644
--- a/logging.go
+++ b/logging.go
@@ -18,7 +18,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"os"
 	"strings"
@@ -630,9 +629,9 @@ func (StderrWriter) OpenWriter() (io.WriteCloser, error) {
 	return notClosable{os.Stderr}, nil
 }
 
-// OpenWriter returns ioutil.Discard that can't be closed.
+// OpenWriter returns io.Discard that can't be closed.
 func (DiscardWriter) OpenWriter() (io.WriteCloser, error) {
-	return notClosable{ioutil.Discard}, nil
+	return notClosable{io.Discard}, nil
 }
 
 // notClosable is an io.WriteCloser that can't be closed.
diff --git a/modules/caddyhttp/replacer.go b/modules/caddyhttp/replacer.go
index d0767f097..4d27a840c 100644
--- a/modules/caddyhttp/replacer.go
+++ b/modules/caddyhttp/replacer.go
@@ -28,7 +28,6 @@ import (
 	"encoding/pem"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net"
 	"net/http"
 	"net/textproto"
@@ -162,7 +161,7 @@ func addHTTPVarsToReplacer(repl *caddy.Replacer, req *http.Request, w http.Respo
 					return "", true
 				}
 				// replace real body with buffered data
-				req.Body = ioutil.NopCloser(buf)
+				req.Body = io.NopCloser(buf)
 				return buf.String(), true
 
 				// original request, before any internal changes
diff --git a/modules/caddyhttp/reverseproxy/fastcgi/client.go b/modules/caddyhttp/reverseproxy/fastcgi/client.go
index 94df0c774..07720539d 100644
--- a/modules/caddyhttp/reverseproxy/fastcgi/client.go
+++ b/modules/caddyhttp/reverseproxy/fastcgi/client.go
@@ -30,7 +30,6 @@ import (
 	"encoding/binary"
 	"errors"
 	"io"
-	"io/ioutil"
 	"mime/multipart"
 	"net"
 	"net/http"
@@ -445,7 +444,7 @@ func (c *FCGIClient) Request(p map[string]string, req io.Reader) (resp *http.Res
 	if chunked(resp.TransferEncoding) {
 		resp.Body = clientCloser{c, httputil.NewChunkedReader(rb)}
 	} else {
-		resp.Body = clientCloser{c, ioutil.NopCloser(rb)}
+		resp.Body = clientCloser{c, io.NopCloser(rb)}
 	}
 	return
 }
diff --git a/modules/caddyhttp/reverseproxy/fastcgi/client_test.go b/modules/caddyhttp/reverseproxy/fastcgi/client_test.go
index f0740a4c8..ef3474d40 100644
--- a/modules/caddyhttp/reverseproxy/fastcgi/client_test.go
+++ b/modules/caddyhttp/reverseproxy/fastcgi/client_test.go
@@ -26,7 +26,6 @@ import (
 	"encoding/binary"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"math/rand"
 	"net"
@@ -166,7 +165,7 @@ func sendFcgi(reqType int, fcgiParams map[string]string, data []byte, posts map[
 	}
 
 	defer resp.Body.Close()
-	content, _ = ioutil.ReadAll(resp.Body)
+	content, _ = io.ReadAll(resp.Body)
 
 	log.Println("c: send data length ≈", length, string(content))
 	fcgi.Close()
diff --git a/modules/caddyhttp/reverseproxy/healthchecks.go b/modules/caddyhttp/reverseproxy/healthchecks.go
index 8d5bd77ec..230bf3aaf 100644
--- a/modules/caddyhttp/reverseproxy/healthchecks.go
+++ b/modules/caddyhttp/reverseproxy/healthchecks.go
@@ -18,7 +18,6 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"net"
 	"net/http"
@@ -282,7 +281,7 @@ func (h *Handler) doActiveHealthCheck(dialInfo DialInfo, hostAddr string, host H
 	}
 	defer func() {
 		// drain any remaining body so connection could be re-used
-		_, _ = io.Copy(ioutil.Discard, body)
+		_, _ = io.Copy(io.Discard, body)
 		resp.Body.Close()
 	}()
 
@@ -313,7 +312,7 @@ func (h *Handler) doActiveHealthCheck(dialInfo DialInfo, hostAddr string, host H
 
 	// if body does not match regex, mark down
 	if h.HealthChecks.Active.bodyRegexp != nil {
-		bodyBytes, err := ioutil.ReadAll(body)
+		bodyBytes, err := io.ReadAll(body)
 		if err != nil {
 			h.HealthChecks.Active.logger.Info("failed to read response body",
 				zap.String("host", hostAddr),
diff --git a/modules/caddyhttp/reverseproxy/httptransport.go b/modules/caddyhttp/reverseproxy/httptransport.go
index 193285138..35bc94783 100644
--- a/modules/caddyhttp/reverseproxy/httptransport.go
+++ b/modules/caddyhttp/reverseproxy/httptransport.go
@@ -20,10 +20,10 @@ import (
 	"crypto/x509"
 	"encoding/base64"
 	"fmt"
-	"io/ioutil"
 	weakrand "math/rand"
 	"net"
 	"net/http"
+	"os"
 	"reflect"
 	"time"
 
@@ -364,7 +364,7 @@ func (t TLSConfig) MakeTLSClientConfig(ctx caddy.Context) (*tls.Config, error) {
 			rootPool.AddCert(caCert)
 		}
 		for _, pemFile := range t.RootCAPEMFiles {
-			pemData, err := ioutil.ReadFile(pemFile)
+			pemData, err := os.ReadFile(pemFile)
 			if err != nil {
 				return nil, fmt.Errorf("failed reading ca cert: %v", err)
 			}
diff --git a/modules/caddyhttp/staticresp_test.go b/modules/caddyhttp/staticresp_test.go
index cd0d1a1e1..5844f43f3 100644
--- a/modules/caddyhttp/staticresp_test.go
+++ b/modules/caddyhttp/staticresp_test.go
@@ -16,7 +16,7 @@ package caddyhttp
 
 import (
 	"context"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"strconv"
@@ -44,7 +44,7 @@ func TestStaticResponseHandler(t *testing.T) {
 	}
 
 	resp := w.Result()
-	respBody, _ := ioutil.ReadAll(resp.Body)
+	respBody, _ := io.ReadAll(resp.Body)
 
 	if resp.StatusCode != http.StatusNotFound {
 		t.Errorf("expected status %d but got %d", http.StatusNotFound, resp.StatusCode)
diff --git a/modules/caddyhttp/templates/tplcontext_test.go b/modules/caddyhttp/templates/tplcontext_test.go
index 1d15ca73b..c2fe61f4c 100644
--- a/modules/caddyhttp/templates/tplcontext_test.go
+++ b/modules/caddyhttp/templates/tplcontext_test.go
@@ -17,7 +17,6 @@ package templates
 import (
 	"bytes"
 	"fmt"
-	"io/ioutil"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -118,7 +117,7 @@ func TestImport(t *testing.T) {
 		// create files for test case
 		if test.fileName != "" {
 			absFilePath := filepath.Join(fmt.Sprintf("%s", context.Root), test.fileName)
-			if err := ioutil.WriteFile(absFilePath, []byte(test.fileContent), os.ModePerm); err != nil {
+			if err := os.WriteFile(absFilePath, []byte(test.fileContent), os.ModePerm); err != nil {
 				os.Remove(absFilePath)
 				t.Fatalf("Test %d: Expected no error creating file, got: '%s'", i, err.Error())
 			}
@@ -198,7 +197,7 @@ func TestInclude(t *testing.T) {
 		// create files for test case
 		if test.fileName != "" {
 			absFilePath := filepath.Join(fmt.Sprintf("%s", context.Root), test.fileName)
-			if err := ioutil.WriteFile(absFilePath, []byte(test.fileContent), os.ModePerm); err != nil {
+			if err := os.WriteFile(absFilePath, []byte(test.fileContent), os.ModePerm); err != nil {
 				os.Remove(absFilePath)
 				t.Fatalf("Test %d: Expected no error creating file, got: '%s'", i, err.Error())
 			}
@@ -357,13 +356,13 @@ func TestFileListing(t *testing.T) {
 
 		// create files for test case
 		if test.fileNames != nil {
-			dirPath, err = ioutil.TempDir(fmt.Sprintf("%s", context.Root), "caddy_ctxtest")
+			dirPath, err = os.MkdirTemp(fmt.Sprintf("%s", context.Root), "caddy_ctxtest")
 			if err != nil {
 				t.Fatalf("Test %d: Expected no error creating directory, got: '%s'", i, err.Error())
 			}
 			for _, name := range test.fileNames {
 				absFilePath := filepath.Join(dirPath, name)
-				if err = ioutil.WriteFile(absFilePath, []byte(""), os.ModePerm); err != nil {
+				if err = os.WriteFile(absFilePath, []byte(""), os.ModePerm); err != nil {
 					os.RemoveAll(dirPath)
 					t.Fatalf("Test %d: Expected no error creating file, got: '%s'", i, err.Error())
 				}
diff --git a/modules/caddypki/crypto.go b/modules/caddypki/crypto.go
index e1a0e354d..d8e72c6d2 100644
--- a/modules/caddypki/crypto.go
+++ b/modules/caddypki/crypto.go
@@ -23,7 +23,7 @@ import (
 	"crypto/x509"
 	"encoding/pem"
 	"fmt"
-	"io/ioutil"
+	"os"
 	"strings"
 )
 
@@ -137,11 +137,11 @@ type KeyPair struct {
 func (kp KeyPair) Load() (*x509.Certificate, interface{}, error) {
 	switch kp.Format {
 	case "", "pem_file":
-		certData, err := ioutil.ReadFile(kp.Certificate)
+		certData, err := os.ReadFile(kp.Certificate)
 		if err != nil {
 			return nil, nil, err
 		}
-		keyData, err := ioutil.ReadFile(kp.PrivateKey)
+		keyData, err := os.ReadFile(kp.PrivateKey)
 		if err != nil {
 			return nil, nil, err
 		}
diff --git a/modules/caddytls/acmeissuer.go b/modules/caddytls/acmeissuer.go
index 9a7e73cd9..42cef0215 100644
--- a/modules/caddytls/acmeissuer.go
+++ b/modules/caddytls/acmeissuer.go
@@ -18,8 +18,8 @@ import (
 	"context"
 	"crypto/x509"
 	"fmt"
-	"io/ioutil"
 	"net/url"
+	"os"
 	"strconv"
 	"time"
 
@@ -152,7 +152,7 @@ func (iss *ACMEIssuer) Provision(ctx caddy.Context) error {
 	if len(iss.TrustedRootsPEMFiles) > 0 {
 		iss.rootPool = x509.NewCertPool()
 		for _, pemFile := range iss.TrustedRootsPEMFiles {
-			pemData, err := ioutil.ReadFile(pemFile)
+			pemData, err := os.ReadFile(pemFile)
 			if err != nil {
 				return fmt.Errorf("loading trusted root CA's PEM file: %s: %v", pemFile, err)
 			}
diff --git a/modules/caddytls/connpolicy.go b/modules/caddytls/connpolicy.go
index 6c7fe3f4e..65cda5fb8 100644
--- a/modules/caddytls/connpolicy.go
+++ b/modules/caddytls/connpolicy.go
@@ -19,7 +19,7 @@ import (
 	"crypto/x509"
 	"encoding/base64"
 	"fmt"
-	"io/ioutil"
+	"os"
 	"strings"
 
 	"github.com/caddyserver/caddy/v2"
@@ -369,7 +369,7 @@ func (clientauth *ClientAuthentication) ConfigureTLSConfig(cfg *tls.Config) erro
 			caPool.AddCert(clientCA)
 		}
 		for _, pemFile := range clientauth.TrustedCACertPEMFiles {
-			pemContents, err := ioutil.ReadFile(pemFile)
+			pemContents, err := os.ReadFile(pemFile)
 			if err != nil {
 				return fmt.Errorf("reading %s: %v", pemFile, err)
 			}
diff --git a/modules/caddytls/fileloader.go b/modules/caddytls/fileloader.go
index fdf54864b..430932b99 100644
--- a/modules/caddytls/fileloader.go
+++ b/modules/caddytls/fileloader.go
@@ -17,7 +17,7 @@ package caddytls
 import (
 	"crypto/tls"
 	"fmt"
-	"io/ioutil"
+	"os"
 
 	"github.com/caddyserver/caddy/v2"
 )
@@ -59,11 +59,11 @@ type CertKeyFilePair struct {
 func (fl FileLoader) LoadCertificates() ([]Certificate, error) {
 	certs := make([]Certificate, 0, len(fl))
 	for _, pair := range fl {
-		certData, err := ioutil.ReadFile(pair.Certificate)
+		certData, err := os.ReadFile(pair.Certificate)
 		if err != nil {
 			return nil, err
 		}
-		keyData, err := ioutil.ReadFile(pair.Key)
+		keyData, err := os.ReadFile(pair.Key)
 		if err != nil {
 			return nil, err
 		}
diff --git a/modules/caddytls/folderloader.go b/modules/caddytls/folderloader.go
index 10b017ee8..0ff0629d9 100644
--- a/modules/caddytls/folderloader.go
+++ b/modules/caddytls/folderloader.go
@@ -19,7 +19,6 @@ import (
 	"crypto/tls"
 	"encoding/pem"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
@@ -79,7 +78,7 @@ func (fl FolderLoader) LoadCertificates() ([]Certificate, error) {
 }
 
 func x509CertFromCertAndKeyPEMFile(fpath string) (tls.Certificate, error) {
-	bundle, err := ioutil.ReadFile(fpath)
+	bundle, err := os.ReadFile(fpath)
 	if err != nil {
 		return tls.Certificate{}, err
 	}