Parsing URLs in Go

Introduction

The purpose of this lab is to demonstrate how to parse URLs in Go.

URL Parsing

The lab requires parsing a sample URL that includes a scheme, authentication info, host, port, path, query params, and query fragment. The parsed URL should be used to extract the individual components of the URL.

• The url and net packages should be imported.
• The sample URL should be parsed and checked for errors.
• The scheme, authentication info, host, port, path, query params, and query fragment should be extracted from the parsed URL.
• The SplitHostPort function should be used to extract the hostname and port from the Host field.
• The ParseQuery function should be used to parse the query params into a map.

## Running our URL parsing program shows all the different
## pieces that we extracted.
$ go run url-parsing.go
postgres
user:pass
user
pass
host.com:5432
host.com
5432
/path
f
k=v
map[k:[v]]
v

There is the full code below:

// URLs provide a [uniform way to locate resources](https://adam.herokuapp.com/past/2010/3/30/urls_are_the_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:pass@host.com: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])
}

Summary

The URL Parsing requires parsing a sample URL and extracting the individual components of the URL. The url and net packages are used to parse and extract the URL components.