Find out available DNS server.
First, you should get a DNS server list from below website.
https://github.com/jedisct1/dnscrypt-proxy/blob/master/dnscrypt-resolvers.csv
Another optional website.
You can execute this command to extract ipv4 address to get sorted and unique result.
grep -o '[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}' dnscrypt-resolvers.csv | sort -nu > server-list.txt
Then execute this command to get available DNS server.
go run dnsexplorer.go < server-list.txt