These steps cover writing and running your application:

1. From your Terminal or console application, create a new directory called ~/projects/go-programming-cookbook/chapter14/fastweb and navigate to this directory.
2. Run this command:

$ go mod init github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter14/fastweb

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

module github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter14/fastweb   

3. Copy tests from ~/projects/go-programming-cookbook-original/chapter14/fastweb, or use this as an exercise to write some of your own code!
4. Create a file called items.go with the following content:

        package main

        import (
            "sync"
        )

        var items []string
        var mu *sync.RWMutex

        func init() {
            mu = &sync.RWMutex{}
        }

        // AddItem adds an item to our list
        // in a thread-safe way
        func AddItem(item string) {
            mu.Lock()
            items = append(items, item)
            mu.Unlock()
        }

        // ReadItems returns our list of items
        // in a thread-safe way
        func ReadItems() []string {
            mu.RLock()
            defer mu.RUnlock()
            return items
        }

5. Create a file called handlers.go with the following content:

        package main

        import (
            "encoding/json"

            "github.com/valyala/fasthttp"
        )

        // GetItems will return our items object
        func GetItems(ctx *fasthttp.RequestCtx) {
            enc := json.NewEncoder(ctx)
            items := ReadItems()
            enc.Encode(&items)
            ctx.SetStatusCode(fasthttp.StatusOK)
        }

        // AddItems modifies our array
        func AddItems(ctx *fasthttp.RequestCtx) {
            item, ok := ctx.UserValue("item").(string)
            if !ok {
                ctx.SetStatusCode(fasthttp.StatusBadRequest)
                return
            }

            AddItem(item)
            ctx.SetStatusCode(fasthttp.StatusOK)
        }

6. Create a file called main.go with the following content:

        package main

        import (
            "fmt"
            "log"

            "github.com/buaazp/fasthttprouter"
            "github.com/valyala/fasthttp"
        )

        func main() {
            router := fasthttprouter.New()
            router.GET("/item", GetItems)
            router.POST("/item/:item", AddItems)

            fmt.Println("server starting on localhost:8080")
            log.Fatal(fasthttp.ListenAndServe("localhost:8080", 
            router.Handler))
        }

7. Run the go build command.
8. Run the ./fastweb command:

$ ./fastweb
server starting on localhost:8080

9. From a separate Terminal, test it our with some curl commands:

$ curl "http://localhost:8080/item/hi" -X POST 

$ curl "http://localhost:8080/item/how" -X POST 

$ curl "http://localhost:8080/item/are" -X POST 

$ curl "http://localhost:8080/item/you" -X POST 

$ curl "http://localhost:8080/item" -X GET 
["hi","how", "are", "you"]

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