The preceding program is trying to implement a REST service using httprouter. We are defining two routes here:

• /api/v1/go-version
• /api/v1/show-file/:name

The :name here is the path parameter. It indicates the API that shows the file named xyz. The basic Go router cannot handle these parameters, by using httprouter, we can also match the REST methods. In the program, we matched GET requests.

In a step-by-step process, the preceding program:

• Imported the httprouter and other necessary Go packages
• Created a new router using the New() method of httprouter
• The router has methods like GET, POST, DELETE, and so on
• The GET method takes two arguments, URL path expression and Handler function
• This router can be passed to the ListenAndServe function of http
• Now, coming to the handlers, they look similar to the ones belonging to ServeMux, but a third argument called httprouter.Params holds information about all parameters that are supplied with a GET request
• We defined the path parameter (a variable in the URL path) called name and used it in our program
• The getCommandOutput function takes commands and arguments and returns output
• The first API calls the Go version and returns the output to the client
• The second API performs a cat command of the file and returns it to the client

Now create two new files in the same directory. These files will be served by our file server program. You can create any custom files in this directory for testing:

Latin.txt:

Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean massa. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Donec quam felis, ultricies nec, pellentesque eu, pretium quis, sem. Nulla consequat massa quis enim. Donec pede justo, fringilla vel, aliquet nec, vulputate eget, arcu.

Greek.txt:

Οἱ δὲ Φοίνιϰες οὗτοι οἱ σὺν Κάδμῳ ἀπιϰόμενοι.. ἐσήγαγον διδασϰάλια ἐς τοὺς ῞Ελληνας ϰαὶ δὴ ϰαὶ γράμματα, οὐϰ ἐόντα πρὶν ῞Ελλησι ὡς ἐμοὶ δοϰέειν, πρῶτα μὲν τοῖσι ϰαὶ ἅπαντες χρέωνται Φοίνιϰες· μετὰ δὲ χρόνου προβαίνοντος ἅμα τῇ ϕωνῇ μετέβαλον ϰαὶ τὸν ϱυϑμὸν τῶν γραμμάτων. Περιοίϰεον δέ σϕεας τὰ πολλὰ τῶν χώρων τοῦτον τὸν χρόνον ῾Ελλήνων ῎Ιωνες· οἳ παραλαβόντες διδαχῇ παρὰ τῶν Φοινίϰων τὰ γράμματα, μεταρρυϑμίσαντές σϕεων ὀλίγα ἐχρέωντο, χρεώμενοι δὲ ἐϕάτισαν, ὥσπερ ϰαὶ τὸ δίϰαιον ἔϕερε ἐσαγαγόντων Φοινίϰων ἐς τὴν ῾Ελλάδα, ϕοινιϰήια ϰεϰλῆσϑαι.

Now run the program with this command. This time, instead of firing a CURL command, let us use the browser as our output for GET. Windows users may not have CURL as the firsthand application. They can use API testing software like the postman client while developing the REST API. Take a look at the following command:

go run execService.go

The output for the first GET request looks like this:

curl -X GET http://localhost:8000/api/v1/go-version

The result will be this:

go version go1.8.3 darwin/amd64

The second GET request requesting Greek.txt is:

curl -X GET http://localhost:8000/api/v1/show-file/greek.txt

Now, we will see the file output in Greek as this:

Οἱ δὲ Φοίνιϰες οὗτοι οἱ σὺν Κάδμῳ ἀπιϰόμενοι.. ἐσήγαγον διδασϰάλια ἐς τοὺς ῞Ελληνας ϰαὶ δὴ ϰαὶ γράμματα, οὐϰ ἐόντα πρὶν ῞Ελλησι ὡς ἐμοὶ δοϰέειν, πρῶτα μὲν τοῖσι ϰαὶ ἅπαντες χρέωνται Φοίνιϰες· μετὰ δὲ χρόνου προβαίνοντος ἅμα τῇ ϕωνῇ μετέβαλον ϰαὶ τὸν ϱυϑμὸν τῶν γραμμάτων. Περιοίϰεον δέ σϕεας τὰ πολλὰ τῶν χώρων τοῦτον τὸν χρόνον ῾Ελλήνων ῎Ιωνες· οἳ παραλαβόντες διδαχῇ παρὰ τῶν Φοινίϰων τὰ γράμματα, μεταρρυϑμίσαντές σϕεων ὀλίγα ἐχρέωντο, χρεώμενοι δὲ ἐϕάτισαν, ὥσπερ ϰαὶ τὸ δίϰαιον ἔϕερε ἐσαγαγόντων Φοινίϰων ἐς τὴν ῾Ελλάδα, ϕοινιϰήια ϰεϰλῆσϑαι.