This example wraps the asynchronous method oauth2.client.getToken(callback) from the package NPM package simple-oauth2into a Fiber so that the method may be called synchronously.

const oauth2 = require('simple-oauth2')(credentials);

const credentials = {
    clientID: '#####',
    clientSecret: '#####',
    site: "API Endpoint Here."
};

Meteor.startup(() => {
    let token = Meteor.wrapAsync(oauth2.client.getToken)({});
    if (token) {
        let headers = {
            'Content-Type': "application/json",
            'Authorization': `Bearer ${token.access_token}`
        }

        // Make use of requested OAuth2 Token Here (Meteor HTTP.get).
    }
});