Http.Get

Go can be used to download web pages. This helps with validating a site works correctly (or for trying to get important data from the web page).

With the net http package, we have many helpful funcs for accessing files through HTTP. We do not need to write any low-level code to do this.

Http.Get example

Let us begin with this example program that uses http.Get. Please note we must import the "net/http" package at the top.

package main

import (
    "fmt"
    "io/ioutil"
    "net/http"
)

func main() {

    // Get Wikipedia home page.
    resp, _ := http.Get("https://en.wikipedia.org/")

    // Defer close the response Body.
    defer resp.Body.Close()

    // Read everything from Body.
    body, _ := ioutil.ReadAll(resp.Body)

    // Convert body bytes to string.
    bodyText := string(body)

    fmt.Println("DONE")
    fmt.Println("Response length: ", len(bodyText))

    // Convert to rune slice to take substring.
    runeSlice := []rune(bodyText)
    fmt.Println("First chars: ", string(runeSlice[0:10]))
}
DONE
Response length:  73727
First chars:  <!DOCTYPE

Status

When a HTTP request is made, the response includes a status code. We can access the string containing the status with "Status."

package main

import (
    "fmt"
    "net/http"
    "strings"
)

func main() {

    // This file does not exist.
    resp, _ := http.Get("https://www.dotnetperls.com/robots.txt")
    defer resp.Body.Close()

    // Test status string.
    fmt.Println("Status:", resp.Status)
    if strings.Contains(resp.Status, "404") {
        fmt.Println("Is not found (string tested)")
    }

    // Test status code of the response.
    fmt.Println("Status code:", resp.StatusCode)
    if resp.StatusCode == 404 {
        fmt.Println("Is not found (int tested)")
    }
}
Status: 404 Not Found
Is not found (string tested)
Status code: 404
Is not found (int tested)

Serve

With the ListenAndServe func, also part of the http module, we can build a simple web server in Go. Each response can have a special function with HandleFunc.

A review

Making sure your website is working correctly is an important job. And Go is well-suited to download pages and validate them.