Source: https://github.com/go-monk/xkcd
My implementation of the Exercise 4.12 from the https://gopl.io:
The popular web comic xkcd has a JSON interface. For example, a request to https://xkcd.com/571/info.0.json produces a detailed description of comic 571, one of many favorites. Download each URL (once!) and build an offline index. Write a tool xkcd that, using this index, prints the URL and transcript of each comic that matches a search term provided on the command line.
$ go install ./cmd/xkcd.go
$ xkcd -h
Usage of xkcd:
-c int
max number of concurrent http requests when building offline index (default 20)
-f string
file holding offline index of comics (default "xkcd.json")
-t print also the transcript
$ xkcd perl
# 181 (2006) Interblag https://xkcd.com/181/
# 208 (2007) Regular Expressions https://xkcd.com/208/
# 224 (2007) Lisp https://xkcd.com/224/
# 312 (2007) With Apologies to Robert Frost https://xkcd.com/312/
# 353 (2007) Python https://xkcd.com/353/
# 407 (2008) Cheap GPS https://xkcd.com/407/
# 519 (2008) 11th Grade https://xkcd.com/519/
# 621 (2009) Superlative https://xkcd.com/621/
#1149 (2012) Broomstick https://xkcd.com/1149/
#1171 (2013) Perl Problems https://xkcd.com/1171/
#1286 (2013) Encryptic https://xkcd.com/1286/
#1306 (2013) Sigil Cycle https://xkcd.com/1306/
#1599 (2015) Water Delivery https://xkcd.com/1599/