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

The io/ioutil package has been deprecated in Go 1.16. 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>

client/config_inspect.go

@@ -4,7 +4,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
-	"io/ioutil"
+	"io"
 
 	"github.com/docker/docker/api/types/swarm"
 )
@@ -23,7 +23,7 @@ func (cli *Client) ConfigInspectWithRaw(ctx context.Context, id string) (swarm.C
 		return swarm.Config{}, nil, wrapResponseError(err, resp, "config", id)
 	}
 
-	body, err := ioutil.ReadAll(resp.body)
+	body, err := io.ReadAll(resp.body)
 	if err != nil {
 		return swarm.Config{}, nil, err
 	}