logs: change timestamp to ISO (#1708)

Co-authored-by: Vishal <vishal-biyani@users.noreply.github.com>

cmd/preupgradechecks/main.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/docopt/docopt-go"
 	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
 
 	"github.com/fission/fission/pkg/info"
 )
@@ -34,7 +35,10 @@ func getStringArgWithDefault(arg interface{}, defaultValue string) string {
 }
 
 func main() {
-	logger, err := zap.NewProduction()
+	config := zap.NewProductionConfig()
+	config.EncoderConfig.EncodeTime = zapcore.ISO8601TimeEncoder
+	logger, err := config.Build()
+
 	if err != nil {
 		log.Fatalf("can't initialize zap logger: %v", err)
 	}