Why is my Go HandleFunc invoked twice when accessed via a web browser?

HandleFunc Invoked Twice

In a simple Go web server example, a puzzling issue arises where the HandleFunc is called twice when accessing port 8000 through a web browser. This differs from the expected behavior when using curl, which triggers only a single invocation.

Unveiling the Issue

Upon implementing a logging statement to troubleshoot the problem, it becomes apparent that an additional request is made by the browser for /favicon.ico. This icon is typically displayed in the address bar of the browser.

Resolution

To resolve this mismatch in request processing, simply acknowledge the request for /favicon.ico in the HandleFunc. If no action is necessary for this specific request, a default empty response can suffice.

Here's the modified code:

package main

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

func hello(w http.ResponseWriter, r *http.Request) {
    io.WriteString(w, "Hello world!")
    log.Println("hello.")
}

func favicon(w http.ResponseWriter, r *http.Request) {
    http.NotFound(w, r)
}

func main() {
    mux := http.NewServeMux()
    mux.HandleFunc("/", hello)
    mux.HandleFunc("/favicon.ico", favicon)
    http.ListenAndServe(":8000", mux)
}

The above is the detailed content of Why is my Go HandleFunc invoked twice when accessed via a web browser?. For more information, please follow other related articles on the PHP Chinese website!