How to handle request methods in Go

Introduction

In the last post we discussed handling request parameters in go. In this post, we’ll go over handling RESTful methods and how to use them with our requests.

Setup

This is what our main.go file looks like:

package main

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

func main() {
  router := http.NewServeMux()

  router.HandleFunc("/ping", func(w http.ResponseWriter, r *http.Request) {
    w.Write([]byte("pong"))
  })

  log.Fatal(http.ListenAndServe(":8080", router))
}

We have a basic /ping route that pongs whenever we hit it. Let’s bind it to a method.

Handling RESTful Methods

ServeMux handler from the net/http package has built in features to handle RESTful Methods.

When defining the route, you simply append the relevant method right in the route pattern:

[METHOD] [HOST]/[PATH]

With all three parts being optional, and / being a valid path. You can read more about this pattern here.

Let’s bind the /ping route to a GET method:

router.HandleFunc("GET /ping", func (w http.ResponseWriter, r *http.Request) {
  fmt.Fprintf(w, "pong")
})

And now to test it out:

iwr http://localhost:8080/ping -Method GET

HTTP/1.1 200 OK
Content-Length: 4
Content-Type: text/plain; charset=utf-8

pong

Great! This works as expected! Now, let’s try making a POST request

iwr http://localhost:8080/ping -Method POST

HTTP/1.1 405 Method Not Allowed
Allow: GET, HEAD
Content-Type: text/plain; charset=utf-8
X-Content-Type-Options: nosniff
Content-Length: 19

Method Not Allowed

You’ll notice it only allows the GET and HEAD requests to this route!

This binding also works with POST, PUT, UPDATE, DELETE, and even custom methods!

Let’s try using a POST method instead of a GET.

router.HandleFunc("POST /ping", func (w http.ResponseWriter, r *http.Request) {
  fmt.Fprintf(w, "pong")
})

Making the POST request again, we get:

iwr http://localhost:8080/ping -Method POST

HTTP/1.1 200 OK
Content-Length: 4
Content-Type: text/plain; charset=utf-8

pong

PS: In case you’re wondering, the methods do need to be in all caps due the HTTP convention. All requests going out have their methods capitalized. Go assumes you’re following convention, and doesn’t automatically captialize the method you set.

And now you know how to handle request methods!