Simplified cloud context creation

cloud_appengine.go

// Contains the App Engine specific cloud utility implementations.
// +build appengine

package cloud

import (
	"net/http"

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

	"appengine"
	"appengine/urlfetch"
)

// Authentication context specific to Google App Engine.
type AuthContext appengine.Context

// NewClient creates an authenticated App Engine HTTP client to access Google
// services.
func NewClient(ctx AuthContext, scopes ...string) *http.Client {
	return &http.Client{
		Transport: &oauth2.Transport{
			Source: google.AppEngineTokenSource(appengine.Context(ctx), scopes...),
			Base: &urlfetch.Transport{
				Context: appengine.Context(ctx),
			},
		},
	}
}

cloud_standalone.go

// Contains the standalone specific cloud utility implementations.
// +build !appengine

package cloud

import (
	"net/http"

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

// Authentication context specific to service accounts.
type AuthContext struct {
	Email      string // Email address of the service account (i.e. "xxx@developer.gserviceaccount.com")
	PrivateKey []byte // The contents of your RSA private key or your PEM file (i.e. []byte("-----BEGIN RSA PRIVATE KEY-----..."))
}

// NewClient creates a service-account authenticated HTTP client to access Google
// services.
func NewClient(ctx AuthContext, scopes ...string) *http.Client {
	auth := &jwt.Config{
		Email:      ctx.Email,
		PrivateKey: ctx.PrivateKey,
		Scopes:     scopes,
		TokenURL:   google.JWTTokenURL,
	}
	return auth.Client(oauth2.NoContext)
}

cloug.go

// Package cloud contains some utility functions for the gcloud-golang project.
package cloud

import (
	"golang.org/x/net/context"
	"google.golang.org/cloud"
)

// NewContext returns a new context that uses the provided authentication context
// to create an authorized HTTP client to access the Google Cloud APIs.
//
// You can obtain the project ID from the Google Developers Console,
// https://console.developers.google.com.
func NewContext(projID string, ctx AuthContext, scopes ...string) context.Context {
	return cloud.NewContext(projID, NewClient(ctx, scopes...))
}