Close outbound output stream properly. fix #1082

common/functions/functions.go

@@ -0,0 +1,23 @@
+package functions
+
+import "v2ray.com/core/common"
+
+// Task is a function that may return an error.
+type Task func() error
+
+// CloseOnSuccess returns a Task to run a follow task if pre-condition passes, otherwise the error in pre-condition is returned.
+func CloseOnSuccess(pre func() error, followup Task) Task {
+	return func() error {
+		if err := pre(); err != nil {
+			return err
+		}
+		return followup()
+	}
+}
+
+// Close returns a Task to close the object.
+func Close(obj interface{}) Task {
+	return func() error {
+		return common.Close(obj)
+	}
+}