func NewSDKConfig(account string) (*SDKConfig, error) {
	configPath, err := sdkConfigPath()
	if err != nil {
		return nil, fmt.Errorf("oauth2/google: error getting SDK config path: %v", err)
	}
	credentialsPath := filepath.Join(configPath, "credentials")
	f, err := os.Open(credentialsPath)
	if err != nil {
		return nil, fmt.Errorf("oauth2/google: failed to load SDK credentials: %v", err)
	}
	defer f.Close()
	var c sdkCredentials
	if err := json.NewDecoder(f).Decode(&c); err != nil {
		return nil, fmt.Errorf("oauth2/google: failed to decode SDK credentials from %q: %v", credentialsPath, err)
	}
	if len(c.Data) == 0 {
		return nil, fmt.Errorf("oauth2/google: no credentials found in %q, run `gcloud auth login` to create one", credentialsPath)
	}
	if account == "" {
		propertiesPath := filepath.Join(configPath, "properties")
		f, err := os.Open(propertiesPath)
		if err != nil {
			return nil, fmt.Errorf("oauth2/google: failed to load SDK properties: %v", err)
		}
		defer f.Close()
		ini, err := internal.ParseINI(f)
		if err != nil {
			return nil, fmt.Errorf("oauth2/google: failed to parse SDK properties %q: %v", propertiesPath, err)
		}
		core, ok := ini["core"]
		if !ok {
			return nil, fmt.Errorf("oauth2/google: failed to find [core] section in %v", ini)
		}
		active, ok := core["account"]
		if !ok {
			return nil, fmt.Errorf("oauth2/google: failed to find %q attribute in %v", "account", core)
		}
		account = active
	}
	for _, d := range c.Data {
		if account == "" || d.Key.Account == account {
			if d.Credential.AccessToken == "" && d.Credential.RefreshToken == "" {
				return nil, fmt.Errorf("oauth2/google: no token available for account %q", account)
			}
			var expiry time.Time
			if d.Credential.TokenExpiry != nil {
				expiry = *d.Credential.TokenExpiry
			}
			return &SDKConfig{
				conf: oauth2.Config{
					ClientID:     d.Credential.ClientID,
					ClientSecret: d.Credential.ClientSecret,
					Scopes:       strings.Split(d.Key.Scope, " "),
					Endpoint:     Endpoint,
					RedirectURL:  "oob",
				},
				initialToken: &oauth2.Token{
					AccessToken:  d.Credential.AccessToken,
					RefreshToken: d.Credential.RefreshToken,
					Expiry:       expiry,
				},
			}, nil
		}
	}
	return nil, fmt.Errorf("oauth2/google: no such credentials for account %q", account)
}
NewSDKConfig creates an SDKConfig for the given Google Cloud SDK
account. If account is empty, the account currently active in
Google Cloud SDK properties is used.
Google Cloud SDK credentials must be created by running `gcloud auth`
before using this function.
The Google Cloud SDK is available at https://cloud.google.com/sdk/.
package google
import (
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"os"
	"os/user"
	"path/filepath"
	"runtime"
	"strings"
	"time"
	"golang.org/x/net/context"
	"golang.org/x/oauth2"
	"golang.org/x/oauth2/internal"
)
type sdkCredentials struct {
	Data []struct {
		Credential struct {
			ClientID     string     `json:"client_id"`
			ClientSecret string     `json:"client_secret"`
			AccessToken  string     `json:"access_token"`
			RefreshToken string     `json:"refresh_token"`
			TokenExpiry  *time.Time `json:"token_expiry"`
		} `json:"credential"`
		Key struct {
			Account string `json:"account"`
			Scope   string `json:"scope"`
		} `json:"key"`
	}
}
type SDKConfig struct {
	conf         oauth2.Config
	initialToken *oauth2.Token
}