Return 401 (UnAuthorized) Status Code in HTTP response in Go (Golang)

Overview

net/http package of golang provides the status code constants which could be used to return different status codes- https://golang.org/src/net/http/status.go

The same can also be used to return the 401 (Unauthorized) HTTP status code.  The HTTP 401 status code is defined by the below constant

http.StatusUnauthorized

In this article, we will also see how to return a JSON body along with the 401 (Unauthorized) Status Code

Program

Below is the program for the same

package main

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

func main() {
	handler := http.HandlerFunc(handleRequest)
	http.Handle("/example", handler)
	http.ListenAndServe(":8080", nil)
}

func handleRequest(w http.ResponseWriter, r *http.Request) {
	w.WriteHeader(http.StatusUnauthorized)
	w.Header().Set("Content-Type", "application/json")
	resp := make(map[string]string)
	resp["message"] = "Unauthorized"
	jsonResp, err := json.Marshal(resp)
	if err != nil {
		log.Fatalf("Error happened in JSON marshal. Err: %s", err)
	}
	w.Write(jsonResp)
	return
}

Here we are using the WriteHeader function to specify the 401 http status code and uses the Write function to also return the response bodyThe above code returns the below JSON request body back in response

{"message":"Unauthorized"}

Run the above program. It will start a server on 8080 port on your local machine. Now make the below curl call to the server

curl -v -X POST http://localhost:8080/example

Below will be the output

* Connected to localhost (::1) port 8080 (#0)
> POST /example HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.54.0
> Accept: */*
> 
< HTTP/1.1 401 Unauthorized
< Date: Sat, 10 Jul 2021 08:19:52 GMT
< Content-Length: 26
< Content-Type: text/plain; charset=utf-8
< 
* Connection #0 to host localhost left intact
{"message":"Unauthorized"}

As you can see from the output, it will correctly return the 401 status code along with the body.

You can also directly pass 401 to the WriteHeader function to send the 401 response.

w.WriteHeader(401)

This also works correctly. Try it out.

Also, check out our Golang advance tutorial Series - Golang Advance Tutorial