Golang : How to validate URL the right way

Validating input from user or external sources is critical and needed to ensure that your program will not simply process 'garbage' data. You know, garbage in, garbage out.

I've seen many programmers use the net/url.Parse() function returning error message as the way to validate URL. However, it is NOT the right way and why you should use a better URL validator, such as govalidator package to validate a URL.

Typically a Golang developer validates an URL with net/url.Parse() function. Such as the code below.

 package main

 import (
 "fmt"
 "net/url"
 )

 func main() {

 str := "//socketloop.com"

 var validURL bool

 _, err := url.Parse(str)

 if err != nil {
 fmt.Println(err)
 validURL = false
 } else {
 validURL = true
 }

 fmt.Printf("%s is a valid URL : %v \n", str, validURL)


 }

This method has many weaknesses and if you change the str value to d or wwwsocketloopcom, net/url.Parse() function will still pass the broken URL as valid. This is NOT the right way to validate URL.

To validate an URL properly, use the IsURL() function from github.com/asaskevich/govalidator package.

 package main

 import (
 "fmt"
 "github.com/asaskevich/govalidator"
 )

 func main() {

 str := "//www.socketloop.com"

 validURL := govalidator.IsURL(str)

 fmt.Printf("%s is a valid URL : %v \n", str, validURL)

 }

Play around by changing the input URL and you will see that this method is more robust than the previous code.

References :

https://github.com/asaskevich/govalidator

http://golang.org/pkg/net/url/#Parse