refactor: move from io/ioutil to io and os package (#2236)

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>

pkg/executor/client/client.go

@@ -20,7 +20,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/url"
 	"strings"
@@ -95,7 +95,7 @@ func (c *Client) GetServiceForFunction(ctx context.Context, fn *fv1.Function) (s
 		return "", ferror.MakeErrorFromHTTP(resp)
 	}
 
-	svcName, err := ioutil.ReadAll(resp.Body)
+	svcName, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return "", errors.Wrap(err, "error reading response body from getting service for function")
 	}