Express: BasicAuth

I'm trying to do some basic authorisation to my the endpoints in an express app using express-basic-auth, but it keeps giving me a 401 unauthorised. I think the headers I'm sending in Post man are incorrect:

Middleware:

app.use(basicAuth({
  users: {'admin': 'supersecret'},
  unauthorizedResponse: 'You are not authorized.'
}));

Postman GET request headers:

Authorization:admin:supersecret

How can I get authorised based on the headers?

Your authorization header should look like this: Authorization: Basic YWRtaW46c3VwZXJzZWNyZXQ=

The last part is the result of encoding admin:supersecret. I just found this tool to generate basic authentication headers, however, Postman can generate the headers itself. Just click on the Authorization option next to Headers and choose Basic Auth.