Cookbooks
Go
Chapter 11. HTML and the Web
Sending an HTTP request

Go:
Sending an HTTP request

How to:

In Go, sending an HTTP request and handling the response involves using the net/http package. Here’s a step-by-step example showing how to send a simple GET request and read the response:

package main

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

func main() {
    // Define the URL of the resource
    url := "http://example.com"

    // Use http.Get to send the GET request
    resp, err := http.Get(url)
    if err != nil {
        log.Fatal(err)
    }
    // Close the response body when the function ends
    defer resp.Body.Close()

    // Read the response body
    body, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        log.Fatal(err)
    }

    // Convert the response body to a string and print it
    fmt.Println(string(body))
}

Sample output (shortened for brevity):

<!doctype html>
<html>
<head>
    <title>Example Domain</title>
...
</html>

To send a POST request with form data, you can use http.PostForm:

package main

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

func main() {
    // Define the URL and form data
    url := "http://example.com/form"
    data := url.Values{}
    data.Set("key", "value")

    // Send the POST request with form data
    resp, err := http.PostForm(url, data)
    if err != nil {
        panic(err)
    }
    defer resp.Body.Close()

    // Read and print the response
    body, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        panic(err)
    }

    fmt.Println(string(body))
}

Deep Dive

The net/http package in Go provides a powerful and flexible way to interact with HTTP servers. Its design reflects Go’s emphasis on simplicity, efficiency, and robustness. Originally, functionalities like handling JSON or XML payloads required manually crafting the request body and setting appropriate headers. As Go evolved, the community has developed higher-level packages that further simplify these tasks, such as gorilla/mux for routing and gjson for JSON manipulation.

One notable aspect of Go’s HTTP client is its use of interfaces and structs, like http.Client and http.Request, which allow for extensive customization and testing. For example, you can modify the http.Client to timeout requests or keep connections alive for performance.

A considered alternative for simpler HTTP interactions is using third-party libraries such as “Resty” or “Gentleman.” These packages offer a more high-level abstraction for HTTP requests, making common tasks more concise. However, understanding and utilizing the underlying net/http package is crucial for dealing with more complex or unique HTTP interaction scenarios, providing a foundation upon which Go’s concurrency features and powerful standard library can be fully leveraged.

Parsing HTMLSending an HTTP request with basic authentication