This is a Go package that facilitates the OAuth2 workflow for a command-line program.

It abstracts the process of running a local web server, listening for a callback/auth code from the authorisation server, and exchanging the auth code for a usable access token.

Existing examples of this process with respect to the command-line are generally based around using the resultant access token within the callback handler itself.

This not only enforces subsequent business logic to be undesirably nested, but also requires that the local web server continues running for the duration of the command-line program.

The goauthcli package encapsulates this process such that the access token is returned to the parent scope following the exchange, so the web server can be shutdown.

This package was written to facilitate the integration of the Spotify Web API within the context of a command-line program.

The following example has therefore been written around this use-case.

The main component is the token.OauthTokenExchanger type, which comprises the following data fields:

• AuthServerRequestURL - string representing the authorisation server's URL for generating an auth code
• Handler - function to act as our token callback handler which accepts a HTTP request sent from the authorisation server (auth code is part of the query string), and returns an access token along with an error
• ListenerPort - port number for the local web server to listen on
• ListenerPath - path/route for our local web server callback handler

You can instantiate a new exchanger using the method token.NewOauthTokenExchanger() which will default ListenerPort to 3000 and ListenerPath to /callback.

1. A new client app has been created at https://developer.spotify.com/
2. There are no other applications listening on port 3000 (this is the package's default but can be overridden as alluded to above)

package main

import (
	"github.com/adamjsc/goauthcli/token"
	"github.com/zmb3/spotify"
	"golang.org/x/oauth2"
	"log"
	"net/http"
)

func main() {
	// get these values from your developer dashboard
	spotifyClientID := "XXX"
	spotifyClientSecret := "XXX"

	// see https://github.com/zmb3/spotify for docs
	auth := spotify.NewAuthenticator(token.GetDefaultCallbackURL(), spotify.ScopeUserReadPrivate)
	auth.SetAuthInfo(spotifyClientID, spotifyClientSecret)

	state := "spotify_example_state" // this value is an additional validation check and can be literally anything 
	url := auth.AuthURL(state)

	// this is our function that will handle the callback from the Spotify authorisation server
	requestHandler := func(r *http.Request) (oauth2.Token, error) {
		token, err := auth.Token(state, r)
		if err != nil {
			return oauth2.Token{}, err
		}

		return *token, err
	}

	// get our access token
	exchanger := token.NewOauthTokenExchanger(url, requestHandler)
	token, err := exchanger.TokenExchange()
	if err != nil {
		log.Fatal(err)
	}

	// see https://github.com/zmb3/spotify for docs
	client := auth.NewClient(&token)
	user, err := client.CurrentUser()
	if err != nil {
		log.Fatal(err)
	}
	log.Printf("Hi %s!\nYour Spotify URI is: %s\n", user.DisplayName, user.URI)
}