Update deprecated io/ioutil functions

ioutil has been deprecated since go 1.16, this fixes all of the
deprecated functions we are using:

ioutil.ReadFile -> os.ReadFile
ioutil.ReadAll -> io.ReadAll
ioutil.WriteFile -> os.WriteFile
ioutil.TempFile -> os.CreateTemp
ioutil.TempDir -> os.MkdirTemp

All of the above are a simple name change, the function arguments and
results are exactly the same as before.

ioutil.ReadDir -> os.ReadDir

now returns a os.DirEntry but the IsDir and Name functions work the
same. The difference is that the FileInfo must be retrieved with the
Info() function which can also return an error.

These were identified by running:
golangci-lint run --build-tags=integration ./...

internal/boot/aws.go

@@ -1,3 +1,4 @@
+//go:build integration
 // +build integration
 
 package boot
@@ -6,7 +7,6 @@ import (
 	"encoding/base64"
 	"errors"
 	"fmt"
-	"io/ioutil"
 	"os"
 
 	"github.com/aws/aws-sdk-go/aws"
@@ -60,7 +60,7 @@ func encodeBase64(input string) string {
 // CreateUserData creates cloud-init's user-data that contains user redhat with
 // the specified public key
 func CreateUserData(publicKeyFile string) (string, error) {
-	publicKey, err := ioutil.ReadFile(publicKeyFile)
+	publicKey, err := os.ReadFile(publicKeyFile)
 	if err != nil {
 		return "", fmt.Errorf("cannot read the public key: %v", err)
 	}

internal/boot/azuretest/azure.go

@@ -1,3 +1,4 @@
+//go:build integration
 // +build integration
 
 package azuretest
@@ -6,7 +7,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"io/ioutil"
 	"log"
 	"net/url"
 	"os"
@@ -137,7 +137,7 @@ func DeleteImageFromAzure(c *azureCredentials, imageName string) error {
 
 // readPublicKey reads the public key from a file and returns it as a string
 func readPublicKey(publicKeyFile string) (string, error) {
-	publicKey, err := ioutil.ReadFile(publicKeyFile)
+	publicKey, err := os.ReadFile(publicKeyFile)
 	if err != nil {
 		return "", fmt.Errorf("cannot read the public key file: %v", err)
 	}

internal/boot/context-managers.go

@@ -1,3 +1,4 @@
+//go:build integration
 // +build integration
 
 package boot
@@ -5,7 +6,6 @@ package boot
 import (
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"os"
 	"os/exec"
@@ -38,9 +38,9 @@ func WithNetworkNamespace(f func(ns NetNS) error) error {
 }
 
 // withTempFile provides the function f with a new temporary file
-// dir and pattern parameters have the same semantics as in ioutil.TempFile
+// dir and pattern parameters have the same semantics as in os.CreateTemp
 func withTempFile(dir, pattern string, f func(file *os.File) error) error {
-	tempFile, err := ioutil.TempFile(dir, pattern)
+	tempFile, err := os.CreateTemp(dir, pattern)
 	if err != nil {
 		return fmt.Errorf("cannot create the temporary file: %v", err)
 	}
@@ -56,7 +56,7 @@ func withTempFile(dir, pattern string, f func(file *os.File) error) error {
 }
 
 func withTempDir(dir, pattern string, f func(dir string) error) error {
-	tempDir, err := ioutil.TempDir(dir, pattern)
+	tempDir, err := os.MkdirTemp(dir, pattern)
 	if err != nil {
 		return fmt.Errorf("cannot create the temporary directory %v", err)
 	}

internal/boot/netns.go

@@ -1,3 +1,4 @@
+//go:build integration
 // +build integration
 
 package boot
@@ -5,7 +6,6 @@ package boot
 import (
 	"context"
 	"fmt"
-	"io/ioutil"
 	"log"
 	"os"
 	"os/exec"
@@ -45,7 +45,7 @@ func newNetworkNamespace() (NetNS, error) {
 		}
 	}
 
-	f, err := ioutil.TempFile(netnsDir, "osbuild-composer-namespace")
+	f, err := os.CreateTemp(netnsDir, "osbuild-composer-namespace")
 	if err != nil {
 		return "", fmt.Errorf("cannot create a tempfile: %v", err)
 	}
@@ -90,7 +90,7 @@ func newNetworkNamespace() (NetNS, error) {
 	if err != nil {
 		return "", fmt.Errorf("cannot set up a loopback device in the new namespace: %v", err)
 	}
-	
+
 	// There's no potential command injection vector here
 	/* #nosec G204 */
 	cmd = exec.Command("mount", "-o", "bind", "/proc/self/ns/net", f.Name())
@@ -134,7 +134,7 @@ func (n NetNS) Path() string {
 // Delete deletes the namespaces
 func (n NetNS) Delete() error {
 	// There's no potential command injection vector here
-        /* #nosec G204 */
+	/* #nosec G204 */
 	cmd := exec.Command("umount", n.Path())
 	cmd.Stderr = os.Stderr
 	cmd.Stdout = os.Stdout

internal/boot/vmwaretest/vmware.go

@@ -1,3 +1,4 @@
+//go:build integration
 // +build integration
 
 package vmwaretest
@@ -5,7 +6,7 @@ package vmwaretest
 import (
 	"errors"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"os"
 	"path/filepath"
 	"strings"
@@ -130,7 +131,7 @@ func runWithStdout(args []string) (string, int) {
 	retcode := cli.Run(args)
 
 	w.Close()
-	out, _ := ioutil.ReadAll(r)
+	out, _ := io.ReadAll(r)
 	os.Stdout = oldStdout
 
 	return strings.TrimSpace(string(out)), retcode