Adding Headers to HTTP Requests in Go

Go has several ways of sending requests, including some convenient methods such as:

• http.Get()
• http.Head()
• http.Post()
• http.PostForm()

However, these don’t let you add headers to requests! If you need customization of the HTTP method or headers, you need to use http.NewRequest().

There are three parts to this:

1. Create a request using http.NewRequest() where you specify the HTTP method and URL
2. Add headers to the request with Header.Set()
3. Send the request using http.Client{}

Here’s a full example:

package main

import (
    "net/http"
)

func main() {
    // create the client that will send the request later
    client := &http.Client{}

    // create a request with NewRequest, specifying HTTP method and URL
    req, err := http.NewRequest("GET", "https://example.com/", nil)
    if err != nil {
        // handle any errors however you'd like
    }

    // add headers to the request
    req.Header.Set("User-Agent", "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:147.0) Gecko/20100101 Firefox/147.0")
    req.Header.Set("Accept-Language", "en-US,en;q=0.9")
    req.Header.Set("Accept-Encoding", "gzip, deflate")
    req.Header.Set("Sec-GPC", "1")
    req.Header.Set("Connection", "keep-alive")

    // use the client to actually send the request
    resp, err := client.Do(req)
    if err != nil {
        // handle any errors however you'd like
    }
    defer resp.Body.Close()
}

Note:

req.Header.Set() can be used to set a header but will _ overwrite _ any existing value for that header.

req.Header.Add() can be used to add a value to a header and will append to any existing value for that header.

For the purposes of this blog post we only need to worry about setting the header once, hence the usage of req.Header.Set().

Similar to my “Using time.Sleep() in Go” post, I wrote this up because the Go docs are too dense and I just needed one full example to understand it and get going.

References

• https://pkg.go.dev/net/http