Package Socket:

- fix tcp,udp,unix socket
- add socket unixgram for session less unix socket
- optmize process & code
- add some standalone test for server / client (add example server config for
  rsyslog)

Package Network/Protocol:
- add unixgram protocol

Package Errors:
- fix bug in loop to prevent circular include

socket/client/unixgram/error.go

@@ -0,0 +1,37 @@
+//go:build linux
+// +build linux
+
+/*
+ * MIT License
+ *
+ * Copyright (c) 2022 Nicolas JUHEL
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ *
+ */
+
+package unixgram
+
+import "fmt"
+
+var (
+	ErrInstance = fmt.Errorf("invalid instance")
+	ErrAddress  = fmt.Errorf("invalid dial address")
+)