Print "Hello World"

We are going to see how to create a simple HTTP server that listens on port 6688. When a request is made to the /helloworld path, the helloworld() function is called. This function simply prints "Hello World" to the response writer.

Create a file main.go

package main

import (
    "fmt"
    "log"
    "net/http"
)
func helloworld(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Hello World")
}

func main() {
    http.HandleFunc("/helloworld", helloworld)
    log.Fatal(http.ListenAndServe(":6688", nil))
}

Here is a more detailed explanation of the code:

• The package main statement tells the Go compiler that this code is in the main package.

• The import statements import the fmt, log, and net/http packages.

• The func helloworld(w http.ResponseWriter, r *http.Request) function is a simple function that prints "Hello World" to the response writer.

• The func main() function is the entry point for the program. It calls the http.HandleFunc() method to tell the HTTP server to handle requests for the /helloworld path with the helloworld() function. It then calls the http.ListenAndServe() method to start the HTTP server.

To run the code, you can save it in a file called main.go and then run the following command:

$ go run main.go

This will start the HTTP server and you can then access it by opening a web browser and navigating to http://localhost:6688/helloworld.

Return JSON

We have seen how to print "Hello world" Now we are going to see how to create a server that when a request is made to the /getbook path, the GetBook() function is called. This function returns a JSON representation of a book object.

Create main1.go

package main

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

type Book struct {
    Title  string `json:"title"`
    Author string `json:"author"`
    Pages  int    `json:"pages"`
}

func GetBook(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "application/json")
    book := Book{
        Title:  "Golang Book",
        Author: "Google",
        Pages:  300,
    }
    json.NewEncoder(w).Encode(book)
}

func main() {
    http.HandleFunc("/getbook", GetBook)
    log.Fatal(http.ListenAndServe(":6688", nil))
}

Here is a more detailed explanation of the code:

• The package main statement tells the Go compiler that this code is in the main package.

• The import statements import the encoding/json, log, and net/http packages.

• The type Book struct statement defines a struct called Book. This struct has three fields: Title, Author, and Pages.

• The func GetBook(w http.ResponseWriter, r *http.Request) function is the function that is called when a request is made to the /getbook path. This function sets the Content-Type header to application/json and then encodes a Book object into JSON and writes it to the response writer.

• The func main() function is the entry point for the program. It calls the http.HandleFunc() method to tell the HTTP server to handle requests for the /getbook path with the GetBook() function. It then calls the http.ListenAndServe()method to start the HTTP server.

To run the code, you can save it in a file called main1.go and then run the following command:

$ go run main1.go

This will start the HTTP server and you can then access it by opening a web browser and navigating to http://localhost:6688/getbook

Thanks for reading

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