rewrite specified domain name record, other domain names are forwarded to the remote server
go run main.go
dig @127.0.0.1 -p 53 test1.test a
;; ANSWER SECTION:
test1.test. 60 IN A 127.0.0.1
dig @127.0.0.1 -p 53 test1.test mx
;; ANSWER SECTION:
my-mail.test. 60 IN MX 10 my-mail.local.