How start web server to open page in browser in golang?

Question

How do I temporarily open a web page in browser using golang?

Like here is how it is done using HTTPServer in python.

Answer 1

Your question is a little misleading as it asks how to open a local page in the web browser, but you actually want to know how to fire up a web server so it can be opened in the browser.

For the latter (firing up a web server to serve static files), you may use the http.FileServer() function. For answers presenting it in greater detail, see: Include js file in Go template and With golang webserver where does the root of the website map onto the filesystem>.

Example serving your /tmp/data folder:

http.Handle("/", http.FileServer(http.Dir("/tmp/data")))
panic(http.ListenAndServe(":8080", nil))

If you want to serve dynamic content (generated by Go code), you can use the net/http package and write your own handler generating the response, e.g.:

func myHandler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprint(w, "Hello from Go")
}

func main() {
    http.HandleFunc("/", myHandler)
    panic(http.ListenAndServe(":8080", nil))
}

As to the first (to open a page in your default browser), there is no builtin support in the Go standard library. But it's not that hard, you just have to execute an OS-specific external command. You may use this cross-platform solution (which I also released in my github.com/icza/gox library, see osx.OpenDefault()):

// open opens the specified URL in the default browser of the user.
func open(url string) error {
    var cmd string
    var args []string

    switch runtime.GOOS {
    case "windows":
        cmd = "cmd"
        args = []string{"/c", "start"}
    case "darwin":
        cmd = "open"
    default: // "linux", "freebsd", "openbsd", "netbsd"
        cmd = "xdg-open"
    }
    args = append(args, url)
    return exec.Command(cmd, args...).Start()
}

This example code is taken from Gowut (which is Go Web UI Toolkit; disclosure: I'm the author).

Note that exec.Command() performs OS-specific argument quoting if needed. So for example if the URL contains &, it will be properly escaped on Linux, however, it might not work on Windows. On Windows you might have to manually quote it yourself, e.g. with replacing & signs with "^&" with a call like strings.ReplaceAll(url, "&", "^&").

Using this to open the previously started webserver in your default browser:

open("http://localhost:8080/")

One last thing to note: http.ListenAndServe() blocks and never returns (if there is no error). So you have to start the server or the browser in another goroutine, for example:

go open("http://localhost:8080/")
panic(http.ListenAndServe(":8080", nil))

Check out this question for other alternatives how to start the browser after the webserver has been started: Go: How can I start the browser AFTER the server started listening?