Connect to Datastore from outside GAE

storage.go

package storage

import (
	"io/ioutil"

	"golang.org/x/net/context"
	"golang.org/x/oauth2/google"
	"google.golang.org/cloud"
	"google.golang.org/cloud/datastore"
)

var ()

// Adaptor is a structure that adapts
type Adaptor struct {
	jsonKeyPath string
	projectID   string
	client      *datastore.Client
}

// HeavyPutter takes a ton of shit and puts something in datastore
func HeavyPutter(jsonKeyFile, projectID, entry string) error {
	jsonKey, err := ioutil.ReadFile(jsonKeyFile)
	if err != nil {
		// log.Fatal(err)
		return err
	}
	conf, err := google.JWTConfigFromJSON(
		jsonKey,
		datastore.ScopeDatastore,
	)
	if err != nil {
		// log.Fatal(err)
		return err
	}
	ctx := context.Background()
	client, err := datastore.NewClient(ctx, projectID, cloud.WithTokenSource(conf.TokenSource(ctx)))
	if err != nil {
		// log.Fatal(err)
		return err
	}

	logEntry := struct {
		log string
	}{
		entry,
	}

	key := datastore.NewIncompleteKey(ctx, "LogEntry", nil)
	_, putErr := client.Put(ctx, key, &logEntry)

	if putErr != nil {
		return putErr
	}

	return nil
}

// CreateAdaptor returns a datastore client built with the right authorization
func CreateAdaptor(jsonKeyFile, projectID string) (*Adaptor, error) {
	jsonKey, err := ioutil.ReadFile(jsonKeyFile)
	if err != nil {
		// log.Fatal(err)
		return nil, err
	}
	conf, err := google.JWTConfigFromJSON(
		jsonKey,
		datastore.ScopeDatastore,
	)
	if err != nil {
		// log.Fatal(err)
		return nil, err
	}
	ctx := context.Background()
	client, err := datastore.NewClient(ctx, projectID, cloud.WithTokenSource(conf.TokenSource(ctx)))
	if err != nil {
		// log.Fatal(err)
		return nil, err
	}

	adaptor := Adaptor{
		jsonKeyFile,
		projectID,
		client,
	}

	// Use the client (see other examples).
	return &adaptor, nil
}

// LogEntry logs entries using a valid client
func (a *Adaptor) LogEntry(entry string) error {

	ctx := context.Background()

	logEntry := struct {
		log string
	}{
		entry,
	}

	key := datastore.NewIncompleteKey(ctx, "LogEntry", nil)
	_, putErr := a.client.Put(ctx, key, &logEntry)

	if putErr != nil {
		return putErr
	}
	return nil
}