all: remove the remaining bits of io/ioutil

The io/ioutil package is deprecated since Go1.16 - see https://tip.golang.org/doc/go1.16#ioutil

VictoriaMetrics requires at least Go1.18, so it is time to remove the io/ioutil from source code

This is a follow-up for 02ca2342ab

app/vmalert/main_test.go

@@ -3,7 +3,6 @@ package main
 import (
 	"context"
 	"fmt"
-	"io/ioutil"
 	"net/url"
 	"os"
 	"testing"
@@ -87,7 +86,7 @@ groups:
 `
 	)
 
-	f, err := ioutil.TempFile("", "")
+	f, err := os.CreateTemp("", "")
 	if err != nil {
 		t.Fatal(err)
 	}

app/vmalert/notifier/config_watcher_test.go

@@ -2,7 +2,6 @@ package notifier
 
 import (
 	"fmt"
-	"io/ioutil"
 	"math/rand"
 	"net/http"
 	"net/http/httptest"
@@ -12,7 +11,7 @@ import (
 )
 
 func TestConfigWatcherReload(t *testing.T) {
-	f, err := ioutil.TempFile("", "")
+	f, err := os.CreateTemp("", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -34,7 +33,7 @@ static_configs:
 		t.Fatalf("expected to have 2 notifiers; got %d %#v", len(ns), ns)
 	}
 
-	f2, err := ioutil.TempFile("", "")
+	f2, err := os.CreateTemp("", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -61,7 +60,7 @@ func TestConfigWatcherStart(t *testing.T) {
 	consulSDServer := newFakeConsulServer()
 	defer consulSDServer.Close()
 
-	consulSDFile, err := ioutil.TempFile("", "")
+	consulSDFile, err := os.CreateTemp("", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -107,7 +106,7 @@ func TestConfigWatcherReloadConcurrent(t *testing.T) {
 	consulSDServer2 := newFakeConsulServer()
 	defer consulSDServer2.Close()
 
-	consulSDFile, err := ioutil.TempFile("", "")
+	consulSDFile, err := os.CreateTemp("", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -123,7 +122,7 @@ consul_sd_configs:
       - consul
 `, consulSDServer1.URL, consulSDServer2.URL))
 
-	staticAndConsulSDFile, err := ioutil.TempFile("", "")
+	staticAndConsulSDFile, err := os.CreateTemp("", "")
 	if err != nil {
 		t.Fatal(err)
 	}

app/vmalert/templates/template.go

@@ -17,7 +17,7 @@ import (
 	"errors"
 	"fmt"
 	htmlTpl "html/template"
-	"io/ioutil"
+	"io"
 	"math"
 	"net"
 	"net/url"
@@ -71,7 +71,7 @@ func Load(pathPatterns []string, overwrite bool) error {
 		}
 	}
 	if len(tmpl.Templates()) > 0 {
-		err := tmpl.Execute(ioutil.Discard, nil)
+		err := tmpl.Execute(io.Discard, nil)
 		if err != nil {
 			return fmt.Errorf("failed to execute template: %w", err)
 		}

app/vmselect/netstorage/tmp_blocks_file.go

@@ -2,7 +2,6 @@ package netstorage
 
 import (
 	"fmt"
-	"io/ioutil"
 	"os"
 	"sync"
 
@@ -109,7 +108,7 @@ func (tbf *tmpBlocksFile) WriteBlockRefData(b []byte) (tmpBlockAddr, error) {
 
 	// Slow path: flush the data from tbf.buf to file.
 	if tbf.f == nil {
-		f, err := ioutil.TempFile(tmpBlocksDir, "")
+		f, err := os.CreateTemp(tmpBlocksDir, "")
 		if err != nil {
 			return addr, err
 		}