add grpc tunnel

pkg/dialer/grpc/metadata.go

@@ -0,0 +1,22 @@
+package grpc
+
+import (
+	mdata "github.com/go-gost/gost/pkg/metadata"
+)
+
+type metadata struct {
+	insecure bool
+	host     string
+}
+
+func (d *grpcDialer) parseMetadata(md mdata.Metadata) (err error) {
+	const (
+		insecure = "grpcInsecure"
+		host     = "host"
+	)
+
+	d.md.insecure = mdata.GetBool(md, insecure)
+	d.md.host = mdata.GetString(md, host)
+
+	return
+}