split the Session.Close(error) in Close() and CloseWithError(error)

benchmark/benchmark_test.go

@@ -79,7 +79,7 @@ func init() {
 					b.RecordValue("transfer rate [MB/s]", float64(dataLen)/1e6/runtime.Seconds())
 
 					ln.Close()
-					sess.Close(nil)
+					sess.Close()
 				}, samples)
 			})
 		}