google-auth

google-auth.go

package main

import (
	"context"
	"fmt"
	"io/ioutil"
	"net/http"

	"golang.org/x/oauth2/google"
)

var (
	scopes = []string{"https://www.googleapis.com/auth/cloud-platform"}
)

func tokenFromEnv() (string, error) {
	ts, err := google.DefaultTokenSource(context.Background(), scopes...)
	if err != nil {
		return "", err
	}

	token, err := ts.Token()
	if err != nil {
		return "", err
	}

	if !token.Valid() {
		return "", fmt.Errorf("token was invalid", nil)
	}

	if token.Type() != "Bearer" {
		return "", fmt.Errorf("expected token type \"Bearer\" but got \"%s\"", token.Type())
	}

	return token.Extra("id_token").(string), nil
}

func main() {
	client := &http.Client{}

	id_token, err := tokenFromEnv()
	if err != nil {
		fmt.Errorf("token: %v", err)
	}
	req, err := http.NewRequest("GET", "https://my-endpoint.example.com/", nil)
	if err != nil {
		fmt.Errorf("req: %v", err)
	}
	req.Header.Add("Authorization", "Bearer "+id_token)

	resp, err := client.Do(req)
	if err != nil {
		fmt.Errorf("Error when calling: %s", err)
	}
	body, _ := ioutil.ReadAll(resp.Body)
	fmt.Printf("Response from server: %s", string(body))
}