Golang : Allow Cross-Origin Resource Sharing request
Problem:
You have a client JavaScript code that want to make XHR(XMLHttpRequest) request to another Golang server which is also controlled by you. However, on the client's browser console shows CORS (Cross-Origin Resource Sharing) error messages. How to fix the issue?
Solution:
Normally, a server should not allow XMLHttpRequest made by another unauthorized client. However, to enable Cross-Origin Resource Sharing, you will need to set the server header with Access-Control-Allow-Origin:*
to the response.
w.Header().Set("Access-Control-Allow-Origin", "*") // usually, this line is enough, but you can add the following options.
If you want to add more specific headers, these are some of the options
w.Header().Set("Access-Control-Allow-Credentials", "true")
w.Header().Set("Access-Control-Allow-Methods", "OPTIONS, GET, POST")
w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Depth, User-Agent, X-File-Size, X-Requested-With, If-Modified-Since, X-File-Name, Cache-Control")
If you're using Nginx, Apache or Caddy as proxy instead of directly serving up from your Golang program. You can add the allow CORS and XHR headers in the proxy server configuration. For example, this tutorial shows how to do that with Caddy. (https://www.socketloop.com/tutorials/golang-setup-api-server-or-gateway-with-caddy-and-http-listenandserve-function-example)
Here you go!
package main
import (
"net/http"
"strings"
)
func SayHelloWorld(w http.ResponseWriter, r *http.Request) {
w.Write([]byte("Hello, World!"))
}
func ReplyName(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Access-Control-Allow-Origin", "*") // usually, this line is enough, but you can add the following options.
w.Header().Set("Access-Control-Allow-Credentials", "true")
w.Header().Set("Access-Control-Allow-Methods", "OPTIONS, GET, POST")
w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Depth, User-Agent, X-File-Size, X-Requested-With, If-Modified-Since, X-File-Name, Cache-Control")
URISegments := strings.Split(r.URL.Path, "/")
if URISegments[2] != "" {
w.Write([]byte(URISegments[2]))
} else {
w.Write([]byte("You gotta give a name for me to reply...."))
}
}
func main() {
// http.Handler
mux := http.NewServeMux()
mux.HandleFunc("/", SayHelloWorld)
mux.HandleFunc("/replyname/", ReplyName)
http.ListenAndServe(":8080", mux)
}
See also : Golang : Setup API server or gateway with Caddy and http.ListenAndServe() function example
By Adam Ng
IF you gain some knowledge or the information here solved your programming problem. Please consider donating to the less fortunate or some charities that you like. Apart from donation, planting trees, volunteering or reducing your carbon footprint will be great too.
Advertisement
Tutorials
+6.2k Javascript : Generate random key with specific length
+7.9k Findstr command the Grep equivalent for Windows
+11.6k Golang : Concurrency and goroutine example
+6k Golang : Dealing with backquote
+14.5k Golang : Missing Bazaar command
+36.5k Golang : Display float in 2 decimal points and rounding up or down
+13.3k Golang : Increment string example
+13.9k Golang : Fix cannot use buffer (type bytes.Buffer) as type io.Writer(Write method has pointer receiver) error
+8.6k Golang : How to join strings?
+18.7k Unmarshal/Load CSV record into struct in Go
+19.1k Golang : Execute shell command
+11.6k Golang : Secure file deletion with wipe example