To run the program you need to install https://golang.org/doc/install first.
$ go get github.com/muravjov/simplednsserver
$ simplednsserver --a-record example.com:1.2.3.4
2019/10/27 22:53:30 simplednsserver listening at :8053...
$ dig @localhost -p 8053 +short example.com
1.2.3.4