Add missing awaits

@@ -3,6 +3,7 @@
 ## 3.6.1
 
 - Update the example to use PdfPreview
+- Add missing `await`s
 
 ## 3.6.0
 

@@ -91,7 +91,7 @@ class MethodChannelPrinting extends PrintingPlatform {
         break;
       case 'onPageRasterEnd':
         final job = _printJobs[call.arguments['job']];
-        job.onPageRasterized.close();
+        await job.onPageRasterized.close();
         _printJobs.remove(job.index);
         break;
     }

@@ -175,7 +175,7 @@ mixin Printing {
     assert(document != null || bytes != null);
     assert(!(document == null && bytes == null));
 
-    layoutPdf(
+    await layoutPdf(
         onLayout: (PdfPageFormat format) =>
             document != null ? document.save() : bytes);
   }