These steps cover writing and running your application:

1. From your Terminal or console application, create a new directory called ~/projects/go-programming-cookbook/chapter2/pipes.
2. Navigate to this directory.
3. Run the following command:

$ go mod init github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter2/pipes

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

module github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter2/pipes   

4. Copy tests from ~/projects/go-programming-cookbook-original/chapter2/pipes, or use this as an opportunity to write some of your own code!
5. Create a file called pipes.go with the following contents:

        package main

        import (
            "bufio"
            "fmt"
            "io"
            "os"
        )

        // WordCount takes a file and returns a map
        // with each word as a key and it's number of
        // appearances as a value
        func WordCount(f io.Reader) map[string]int {
            result := make(map[string]int)

            // make a scanner to work on the file
            // io.Reader interface
            scanner := bufio.NewScanner(f)
            scanner.Split(bufio.ScanWords)

            for scanner.Scan() {
                result[scanner.Text()]++
            }

            if err := scanner.Err(); err != nil {
                fmt.Fprintln(os.Stderr, "reading input:", err)
            }

            return result
        }

        func main() {
            fmt.Printf("string: number_of_occurrences

")
            for key, value := range WordCount(os.Stdin) {
                fmt.Printf("%s: %d
", key, value)
            }
        }

6. Run echo "some string" | go run pipes.go.
7. You may also run the following commands:

$ go build
echo "some string" | ./pipes

You should see the following output:

$ echo "test case" | go run pipes.go
string: number_of_occurrences

test: 1
case: 1

$ echo "test case test" | go run pipes.go
string: number_of_occurrences

test: 2
case: 1

8. If you copied or wrote your own tests, go up one directory and run go test. Ensure that all the tests pass.