Make the expires option set Expires and Cache-Control headers

options/processing_options.go

@@ -95,6 +95,8 @@ type ProcessingOptions struct {
 
 	CacheBuster string
 
+	Expires *time.Time
+
 	Watermark WatermarkOptions
 
 	PreferWebP  bool
@@ -826,6 +828,9 @@ func applyExpiresOption(po *ProcessingOptions, args []string) error {
 		return errExpiredURL
 	}
 
+	expires := time.Unix(timestamp, 0)
+	po.Expires = &expires
+
 	return nil
 }