This chapter is from the book
This chapter is from the book
This chapter is from the book
Handling 404s
The behavior of the default Handler is to pass any request that does not have a handler function defined to /. Returning to the first example, if a request is made to a non-existent page, the handler function for / is called, and a 200 along with the “Hello World” response is returned.
curl -is http://localhost:8000/asdfa HTTP/1.1 200 OK Date: Thu, 17 Nov 2016 09:07:51 GMT Content-Length: 12 Content-Type: text/plain; charset=utf-8
As the route does not exist, a 404 Page Not Found should be returned. On the default route, a check can be added to return a 404 if the path is not / (see Listing 18.2).
LISTING 18.2 Adding a 404 Response
1: package main
2:
3: import (
4: "net/http"
5: )
6:
7: func helloWorld(w http.ResponseWriter, r *http.Request) {
8: if r.URL.Path != "/" {
9: http.NotFound(w, r)
10: return
11: }
12: w.Write([]byte("Hello World\n"))
13: }
14:
15: func main() {
16: http.HandleFunc("/", helloWorld)
17: http.ListenAndServe(":8000", nil)
18: }
The modifications to the initial Hello World web server may be explained as follows:
In the helloWorld handler function, the path is checked to see if it is /.
If it is not, the NotFound method from the http package is called, passing the response and request. This writes a 404 response to the client.
If the path does match /, then the if statement is ignored and the Hello World response is sent.