Unforatunately, I haven't figure out how to port this over to Now V2 since they no longer support running arbitrary Docker containers. This will not work unless you have an older now.sh account that has been grandfathered in to still supporting V1.
This example compiles and installs massdns inside a Docker container running the Micro webserver. The webserver reads data from POST request bodies, writes it to a temp file, and executes massdns against it like so:
massdns -r /massdns-master/lists/resolvers.txt -o J ${tmpdir}/domains.txt
Stdout from the process is massaged a little bit to make well-formed JSON, and then the response is returned in an HTTP response.
This is more of a PoC of what is possible with serverless container execution. I'd probably rather just rather run massdns in a container locally, but if you ever find yourself needing to resolve a lot of domain names and only have the ability to make HTTP requests, this might be useful
$ now --public
Select [2] Dockerfile for deployment type
You must POST a file with domain names on each line. The easiest way is with curl:
$ curl -s -X POST --data-binary "@domains.txt" https://massdns-gingahvmrz.now.sh
This will return JSON that can be parsed with jq or your tool of choice.