Add NewErrorAsyncJobInProgress func (#565)

Author: jwierzbo

util/connection/wrappers/async/async.go

@@ -65,7 +65,7 @@ func (a asyncConnectionWrapper) Do(ctx context.Context, req driver.Request) (dri
 			}
 
 			// Job is in progress
-			return nil, ErrorAsyncJobInProgress{id}
+			return nil, NewErrorAsyncJobInProgress(id)
 		default:
 			return resp, nil
 		}
@@ -83,7 +83,7 @@ func (a asyncConnectionWrapper) Do(ctx context.Context, req driver.Request) (dri
 			if asyncID := resp.Header(ArangoHeaderAsyncIDKey); len(asyncID) == 0 {
 				return nil, errors.New("missing async key response")
 			} else {
-				return nil, ErrorAsyncJobInProgress{asyncID}
+				return nil, NewErrorAsyncJobInProgress(asyncID)
 			}
 		default:
 			// we expect a 202 status code only

util/connection/wrappers/async/async_errors.go

@@ -41,6 +41,12 @@ type ErrorAsyncJobInProgress struct {
 	jobID string
 }
 
+func NewErrorAsyncJobInProgress(jobID string) ErrorAsyncJobInProgress {
+	return ErrorAsyncJobInProgress{
+		jobID: jobID,
+	}
+}
+
 func (a ErrorAsyncJobInProgress) Error() string {
 	return fmt.Sprintf("Job with ID %s in progress", a.jobID)
 }