The following steps cover the writing and running of your application:

1. From your Terminal or console application, create a new directory called ~/projects/go-programming-cookbook/chapter8/handlers, and navigate to this directory.

2. Run the following command:

$ go mod init github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter8/handlers

You should see a file called go.mod that contains the following:

module github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter8/handlers    

3. Copy tests from ~/projects/go-programming-cookbook-original/chapter8/handlers, or use this as an exercise to write some of your own code!
4. Create a file called get.go with the following contents:

        package handlers

        import (
            "fmt"
            "net/http"
        )

        // HelloHandler takes a GET parameter "name" and responds
        // with Hello <name>! in plaintext
        func HelloHandler(w http.ResponseWriter, r *http.Request) {
            w.Header().Set("Content-Type", "text/plain")
            if r.Method != http.MethodGet {
                w.WriteHeader(http.StatusMethodNotAllowed)
                return
            }
            name := r.URL.Query().Get("name")

            w.WriteHeader(http.StatusOK)
            w.Write([]byte(fmt.Sprintf("Hello %s!", name)))
        }

5. Create a file called post.go with the following contents:

        package handlers

        import (
            "encoding/json"
            "net/http"
        )

        // GreetingResponse is the JSON Response that
        // GreetingHandler returns
        type GreetingResponse struct {
            Payload struct {
                Greeting string `json:"greeting,omitempty"`
                Name string `json:"name,omitempty"`
                Error string `json:"error,omitempty"`
            } `json:"payload"`
            Successful bool `json:"successful"`
        }

        // GreetingHandler returns a GreetingResponse which either has 
        // errors or a useful payload
        func GreetingHandler(w http.ResponseWriter, r *http.Request) {
            w.Header().Set("Content-Type", "application/json")
            if r.Method != http.MethodPost {
                w.WriteHeader(http.StatusMethodNotAllowed)
                return
            }
            var gr GreetingResponse
            if err := r.ParseForm(); err != nil {
                gr.Payload.Error = "bad request"
                if payload, err := json.Marshal(gr); err == nil {
                    w.Write(payload)
                }  else if err != nil {
                    w.WriteHeader(http.StatusInternalServerError)
                }
            }
            name := r.FormValue("name")
            greeting := r.FormValue("greeting")

            w.WriteHeader(http.StatusOK)
            gr.Successful = true
            gr.Payload.Name = name
            gr.Payload.Greeting = greeting
            if payload, err := json.Marshal(gr); err == nil {
               w.Write(payload)
            }
        }

6. Create a new directory named example and navigate to it.
7. Create a file called main.go with the following contents:

        package main

        import (
            "fmt"
            "net/http"

            "github.com/PacktPublishing/
             Go-Programming-Cookbook-Second-Edition/
             $ chapter8/handlers"
        )

        func main() {
            http.HandleFunc("/name", handlers.HelloHandler)
            http.HandleFunc("/greeting", handlers.GreetingHandler)
            fmt.Println("Listening on port :3333")
            err := http.ListenAndServe(":3333", nil)
            panic(err)
        }

8. Run go run main.go.
9. You could also run the following command:

$ go build
$ ./example

You should see the following output:

$ go run main.go
Listening on port :3333

10. In a separate Terminal, run the following commands:

$ curl "http://localhost:3333/name?name=Reader" -X GET 
$ curl "http://localhost:3333/greeting" -X POST -d  
 'name=Reader;greeting=Goodbye'

You should see the following output:

$ curl "http://localhost:3333/name?name=Reader" -X GET 
Hello Reader!

$ curl "http://localhost:3333/greeting" -X POST -d 'name=Reader;greeting=Goodbye' 
{"payload":{"greeting":"Goodbye","name":"Reader"},"successful":true}

11. The go.mod file may be updated and the go.sum file should now be present in the top-level recipe directory.
12. If you copied or wrote your own tests, go up one directory and run go test. Ensure that all tests pass.