Grasp

Grasp is a tiny command line utility to generate MD5 digest for website addresses.

Overview

I tried to be simple, but correct, using only the standard library, as requested by the challenge description. The entire code is in a single file, called grasp.go. There are three functions, besides main:

normalizeAddresses to add http to the addresses whenever it is necessary
fetcher the worker itself, it fetches the body and publishes the MD5 digest
run to isolate the code execution from main

Workers, channels, and synchronization

There are two types of workers here

fetcher to retrieve the page and calculate the MD5
printer to print out the addresses and their MD5 values

The communication happens using two channels

inputChannel receives the normalized URLs passed as arguments from command line
printChannel receives the digest version of the response body

The synchronization happens using two wait groups

wgFetcher ensures that only after finishing fetching we may close the print channel
wgPrinter ensures that we wait for all the messages to be print before moving on with the execution

Error messages

For simplicity, grasp does not use another channel to send out error messages, every error is sent out using the same print channel.

Do not add any extra features

If I were to add a couple of flags, I would definitely add one to control the length of the input channel buffer, and another one to control the length of the print channel buffer. Also, having a way to control the amount of printer workers would be interesting. This way you would have all the buttons and knobs to change and see what variables play the most important roles here.

Running

In order to run this challenge, please, move to a temporary directory, clone this repository, build and run it. The process may change from environment to environment, but it should be something like this: