TTuck
Encoding · Example 63

URL Parsing

fmt net net/url

URLs provide a uniform way to locate resources. Here's how to parse URLs in Go.

package main

import (
	"fmt"
	"net"
	"net/url"
)

func main() {

We'll parse this example URL, which includes a scheme, authentication info, host, port, path, query params, and query fragment.

	s := "postgres://user:[email protected]:5432/path?k=v#f"

Parse the URL and ensure there are no errors.

	u, err := url.Parse(s)
	if err != nil {
		panic(err)
	}

Accessing the scheme is straightforward.

	fmt.Println(u.Scheme)

User contains all authentication info; call Username and Password on this for individual values.

	fmt.Println(u.User)
	fmt.Println(u.User.Username())
	p, _ := u.User.Password()
	fmt.Println(p)

The Host contains both the hostname and the port, if present. Use SplitHostPort to extract them.

	fmt.Println(u.Host)
	host, port, _ := net.SplitHostPort(u.Host)
	fmt.Println(host)
	fmt.Println(port)

Here we extract the path and the fragment after the #.

	fmt.Println(u.Path)
	fmt.Println(u.Fragment)

To get query params in a string of k=v format, use RawQuery. You can also parse query params into a map. The parsed query param maps are from strings to slices of strings, so index into [0] if you only want the first value.

	fmt.Println(u.RawQuery)
	m, _ := url.ParseQuery(u.RawQuery)
	fmt.Println(m)
	fmt.Println(m["k"][0])

Building URLs: url.Values encodes query strings, and QueryEscape escapes a single value.

	q := url.Values{}
	q.Set("q", "go by example")
	q.Add("tag", "std")
	q.Add("tag", "net/url")
	built := url.URL{Scheme: "https", Host: "example.com", Path: "/search", RawQuery: q.Encode()}
	fmt.Println(built.String())
	fmt.Println(url.QueryEscape("a b&c"), url.PathEscape("a b/c"))

ResolveReference resolves a relative link against a base URL.

	base, _ := url.Parse("https://example.com/docs/intro/")
	ref, _ := url.Parse("../api?v=2")
	fmt.Println(base.ResolveReference(ref))
}
$ go run ./63_url_parsing
postgres
user:pass
user
pass
host.com:5432
host.com
5432
/path
f
k=v
map[k:[v]]
v
https://example.com/search?q=go+by+example&tag=std&tag=net%2Furl
a+b%26c a%20b%2Fc
https://example.com/docs/api?v=2
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