add sshd listener

pkg/handler/sshd/metadata.go

@@ -0,0 +1,12 @@
+package ssh
+
+import (
+	mdata "github.com/go-gost/gost/pkg/metadata"
+)
+
+type metadata struct {
+}
+
+func (h *forwardHandler) parseMetadata(md mdata.Metadata) (err error) {
+	return
+}