refactor: move from io/ioutil to io and os package

The io/ioutil package has been deprecated as of Go 1.16, see
https://golang.org/doc/go1.16#ioutil. This commit replaces the existing
io/ioutil functions with their new definitions in io and os packages.

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

storage/sql/config.go

@@ -5,8 +5,8 @@ import (
 	"crypto/x509"
 	"database/sql"
 	"fmt"
-	"io/ioutil"
 	"net"
+	"os"
 	"regexp"
 	"strconv"
 	"strings"
@@ -320,7 +320,7 @@ func (s *MySQL) makeTLSConfig() error {
 	cfg := &tls.Config{}
 	if s.SSL.CAFile != "" {
 		rootCertPool := x509.NewCertPool()
-		pem, err := ioutil.ReadFile(s.SSL.CAFile)
+		pem, err := os.ReadFile(s.SSL.CAFile)
 		if err != nil {
 			return err
 		}