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This guide demonstrates how to integrate Auth0 with any new or existing Go API application using the go-jwt-middleware package.If you have not created an API in your Auth0 dashboard yet, use the interactive selector to create a new Auth0 API or select an existing API for your project.To set up your first API through the Auth0 dashboard, review our getting started guide.Each Auth0 API uses the API Identifier, which your application needs to validate the access token.
New to Auth0? Learn how Auth0 works and read about implementing API authentication and authorization using the OAuth 2.0 framework.
1

Define permissions

Permissions let you define how resources can be accessed on behalf of the user with a given access token. For example, you might choose to grant read access to the messages resource if users have the manager access level, and a write access to that resource if they have the administrator access level.You can define allowed permissions in the Permissions view of the Auth0 Dashboard’s APIs section. The following example uses the read:messages scope.
2

Install dependencies

Add a go.mod file to list all the necessary dependencies.
// go.mod
module 01-Authorization-RS256
go 1.21
require (
github.com/auth0/go-jwt-middleware/v2 v2.2.0

github.com/joho/godotenv v1.5.1

)
Download dependencies by running the following shell command:
go mod download
3

Configure your application

Create a .env file within the root of your project directory to store the app configuration. Then, fill in the environment variables:To configure this snippet
# The URL of our Auth0 Tenant Domain.
If you're using a Custom Domain, be sure to set this to that value instead.
AUTH0_DOMAIN='dev-gja8kxz4ndtex3rq.us.auth0.com'
Our Auth0 API's Identifier.
AUTH0_AUDIENCE='{yourApiIdentifier}'
4

Create a middleware to validate access tokens

The EnsureValidToken middleware function validates the access token. You can apply this function to any endpoints you wish to protect. If the token is valid, the endpoint releases the resources. If the token is not valid, the API returns a 401 Authorization error.Set up the go-jwt-middleware middleware to verify access tokens from incoming requests.By default, your API will be set up to use RS256 as the algorithm for signing tokens. Since RS256 works by using a private/public keypair, tokens can be verified against the public key for your Auth0 account. This public key is accessible at https://dev-gja8kxz4ndtex3rq.us.auth0.com/.well-known/jwks.json.Include a mechanism to check that the token has sufficient scope to access the requested resources.Create a function HasScope to check and ensure the access token has the correct scope before returning a successful response.
5

Protect API endpoints

In this example, create an /api/public endpoint that does not use the EnsureToken middleware as it is accessible to non-authenticated requests.Create an /api/private endpoint that requires the EnsureToken middleware as it is only available to authenticated requests containing an access token with no additional scope.Create an /api/private-scoped endpoint that requires the EnsureToken middleware and HasScope as it is only available for authenticated requests containing an access token with the read:messages scope granted.
Only the read:messages scope is checked by the HasScope function. You may want to extend it or make it a standalone middleware that accepts multiple scopes to fit your use case.

​
Make a Call to Your API

To make calls to your API, you need an Access Token. You can get an Access Token for testing purposes from the Test view in your API settings.
Provide the Access Token as an Authorization header in your requests.
curl --request get \
--url 'http:///%7ByourDomain%7D/api_path' \
--header 'authorization: Bearer YOUR_ACCESS_TOKEN_HERE'
Checkpoint
Now that you have configured your application, run your application and verify that:
  • GET /api/publicis available for non-authenticated requests.
  • GET /api/privateis available for authenticated requests.
  • GET /api/private-scopedis available for authenticated requests containing an access token with the read:messagesscope.

​
Next Steps

Excellent work! If you made it this far, you should now have login, logout, and user profile information running in your application.This concludes our quickstart tutorial, but there is so much more to explore. To learn more about what you can do with Auth0, check out:
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