Merge pull request chai2010#493 from crcms/master

Update ch4-05-grpc-hack.md

Author: chai2010

ch4-rpc/ch4-05-grpc-hack.md

@@ -293,7 +293,7 @@ func filter(ctx context.Context,
 	req interface{}, info *grpc.UnaryServerInfo,
 	handler grpc.UnaryHandler,
 ) (resp interface{}, err error) {
-	log.Println("fileter:", info)
+	log.Println("filter:", info)
 	return handler(ctx, req)
 }
 ```
@@ -318,7 +318,7 @@ func filter(
 	info *grpc.UnaryServerInfo,
 	handler grpc.UnaryHandler,
 ) (resp interface{}, err error) {
-	log.Println("fileter:", info)
+	log.Println("filter:", info)
 
 	defer func() {
 		if r := recover(); r != nil {