add sni handler

pkg/handler/sni/metadata.go

@@ -0,0 +1,23 @@
+package sni
+
+import (
+	"time"
+
+	md "github.com/go-gost/gost/pkg/metadata"
+)
+
+type metadata struct {
+	readTimeout time.Duration
+	retryCount  int
+}
+
+func (h *sniHandler) parseMetadata(md md.Metadata) (err error) {
+	const (
+		readTimeout = "readTimeout"
+		retryCount  = "retry"
+	)
+
+	h.md.readTimeout = md.GetDuration(readTimeout)
+	h.md.retryCount = md.GetInt(retryCount)
+	return
+}