fix #418: use struct.asMap() for data field (#638)

Co-authored-by: Bo-Yi Wu <appleboy.tw@gmail.com>

rpc/server.go

@@ -2,6 +2,7 @@ package rpc
 
 import (
 	"context"
+	"fmt"
 	"net"
 	"strings"
 	"sync"
@@ -97,8 +98,8 @@ func (s *Server) Send(ctx context.Context, in *proto.NotificationRequest) (*prot
 
 	if in.Data != nil {
 		notification.Data = map[string]interface{}{}
-		for k, v := range in.Data.Fields {
-			notification.Data[k] = v
+		for k, v := range in.Data.AsMap() {
+			notification.Data[k] = fmt.Sprintf("%v", v)
 		}
 	}