lib2.go

package mylib

import "net/http"

// New create a new Instance of mylib
func New(someAlwaysRequiredValue string) (*Instance, error) {
	return &Instance{
		client: new(http.Client), // default no auth client
	}, nil
}

type Instance struct {
	client *http.Client
}

// BasicAuth sets the username and password for requests.
func (i *Instance) BasicAuth(username, password string) error {
	// create an http client where the basic credentials
	// are injected automatically into requests.
	client,err := //...
	if err != nil {
		return err
	}
	i.client = client
	return nil
}

// OAuth ...
func (i *Instance) OAuth(id, secret string) error{
	// ....
	return nil
}