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/controller/httpTriggerApi.go

@@ -20,7 +20,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"sort"
 
@@ -158,7 +158,7 @@ func (a *API) checkHTTPTriggerDuplicates(ctx context.Context, t *fv1.HTTPTrigger
 }
 
 func (a *API) HTTPTriggerApiCreate(w http.ResponseWriter, r *http.Request) {
-	body, err := ioutil.ReadAll(r.Body)
+	body, err := io.ReadAll(r.Body)
 	if err != nil {
 		a.respondWithError(w, err)
 		return
@@ -228,7 +228,7 @@ func (a *API) HTTPTriggerApiUpdate(w http.ResponseWriter, r *http.Request) {
 	vars := mux.Vars(r)
 	name := vars["httpTrigger"]
 
-	body, err := ioutil.ReadAll(r.Body)
+	body, err := io.ReadAll(r.Body)
 	if err != nil {
 		a.respondWithError(w, err)
 		return