fix get image error.

StationProbe/ProbeTask.cs

@@ -424,7 +424,7 @@ namespace StationProbe
             }
         }
 
-        private async void DoSaveExamImageAsync(IPage page, string examId, int imageIndex, string imageUrl)
+        private async void DoSaveExamImageAsync(IPage page, string examId, int imageIndex, string imageUrl, ManualResetEvent finishEvent)
         {
             var response = await page.WaitForResponseAsync(imageUrl);
             var imageData = await response.BufferAsync();
@@ -438,14 +438,19 @@ namespace StationProbe
             };
             _examStore.AddImage(image);
             Logger.WriteLine($"Image:{imageUrl} stored.");
+            finishEvent.Set();
         }
 
         private async Task SaveExamImageAsync(IPage page, string examId, int imageIndex, string imageUrl)
         {
             await using (var imagePage = await page.Browser.NewPageAsync())
             {
-                DoSaveExamImageAsync(imagePage, examId, imageIndex, imageUrl);
+                var finishEvent = new ManualResetEvent(false);
+                finishEvent.Reset();
+                DoSaveExamImageAsync(imagePage, examId, imageIndex, imageUrl, finishEvent);
                 await imagePage.GoToAsync(imageUrl);
+                finishEvent.WaitOne();
+                finishEvent.Dispose();
             }
         }