add protocol option for node

chain/hop.go

@@ -3,8 +3,9 @@ package chain
 import "context"
 
 type SelectOptions struct {
-	Addr string
-	Host string
+	Addr     string
+	Host     string
+	Protocol string
 }
 
 type SelectOption func(*SelectOptions)
@@ -21,6 +22,12 @@ func HostSelectOption(host string) SelectOption {
 	}
 }
 
+func ProtocolSelectOption(protocol string) SelectOption {
+	return func(o *SelectOptions) {
+		o.Protocol = protocol
+	}
+}
+
 type Hop interface {
 	Nodes() []*Node
 	Select(ctx context.Context, opts ...SelectOption) *Node