feat: add plugin

ext/custom/.gitignore

@@ -0,0 +1,2 @@
+*
+!.gitignore

ext/init.go

@@ -0,0 +1,24 @@
+package ext
+
+import (
+	"os"
+	"plugin"
+
+	"github.com/sirupsen/logrus"
+)
+
+const (
+	TRSPluginFile = "./terasu.plugin.so"
+)
+
+func init() {
+	if _, err := os.Stat(TRSPluginFile); err != nil {
+		return
+	}
+	_, err := plugin.Open(TRSPluginFile)
+	if err != nil {
+		logrus.Warnln("[terasu.plugin] load", TRSPluginFile, "err:", err)
+		logrus.Warnln("[terasu.plugin] hint: ensure the main binary and plugin are built with identical flags (e.g. both use -trimpath -ldflags=\"-s -w\"), and avoid using 'go run'")
+		return
+	}
+}