Go Routing Path Values

19 Apr 2024

Go 1.22 Routing Enhancements include improvements to deal with Path Values.

This post is intended for developers who have a basic knowledge of HTML and Go. It serves purely as an example for educational purposes only and it should not be used in production.

Package Name and Imports

Set the package name and the import used in the following code.

package main

import (
	"fmt"
	"html/template"
	"log"
	"net/http"
)

Constants

These values can be changed to suit your needs.

const host = "127.0.0.1:8888"

const appTitle = "Routing Path Values"

const contentTypeTextHTML string = "text/html; charset=UTF-8"

Main Function

This function sets up the HTTP Server and routes.

func main() {

	var httpServer *http.Server

	router := http.NewServeMux()

	router.HandleFunc("/", RouteHandler)
	router.HandleFunc("/route/{pathValue}", RouteHandler)

	log.Printf(`Starting %s http://%s`, appTitle, host)

	httpServer = &http.Server{
		Addr:    host,
		Handler: router,
	}

	err := httpServer.ListenAndServe()

	if err != nil {
		log.Fatalf("ListenAndServe(): %s", err)
	}
}

RouteHandler

This function outputs html with two buttons. Each button makes a request with different Path Values.

If a non-blank Path Value is received it is display at the bottom of the page.

func RouteHandler(responseWriter http.ResponseWriter, httpRequest *http.Request) {

	responseWriter.Header().Set("Content-Type", contentTypeTextHTML)

	pathValue := httpRequest.PathValue("pathValue")

	escapedPathString := ""

	if pathValue != "" {
		escapedPathString = template.HTMLEscapeString(fmt.Sprintf(`Path Value = "%s"`, pathValue))
	}

	htmlTemplate := `
	<html>
	<body>
	<form name="form1" action="/route/route1" method="post">
	<button>Route 1</button>
	</form>
	<form name="form2" action="/route/route2" method="post">
	<button>Route 2</button>
	</form>
	<div>%s</div>
	</body>
	</html>
	`

	fmt.Fprint(responseWriter, fmt.Sprintf(htmlTemplate, escapedPathString))
}

Troubleshooting

When I was first tested this code, it did not detect the Path Values correctly. After a Google search and checking coding forums which advised checking the version in the “go.mod” and “go.work” files in the project. I found that these files had not been updated when I installed the new version of Golang. After correcting this issue, the code worked correctly.