In this chapter, we learned how five small command-line programs can, when composed together, produce powerful results while remaining modular. We avoided tightly coupling our programs so they are still useful in their own right. For example, we can use our available program just to check if domain names we manually enter are available or not, or we can use our synonyms program just as a command-line thesaurus.

We learned how standard streams could be used to build different flows of these types of programs, and how redirection of the standard input and the standard output lets us play around with different flows very easily.

We learned how simple it is in Go to consume a JSON RESTful APIs web service when we needed to get synonyms from the Big Hugh Thesaurus. We kept it simple at first by coding it inline and later refactoring the code to abstract the Thesaurus type into its own package, which is ready to share. We also consumed a non-HTTP API when we opened a connection to the WHOIS server and wrote data over raw TCP.

We saw how the math/rand package can bring a little variety and unpredictability, by allowing us to use pseudo random numbers and decisions in our code, which meant that each time we run our program, we get different results.

Finally, we built our domainfinder super program that composes all the subprograms together giving our solution a simple, clean, and elegant interface.