问错误400 oauth2谷歌云存储- go lang

EN

// datastore1
package main

import (
  "fmt"
  "io/ioutil"
  "log"
  "time"

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

const (
// ScopeDatastore grants permissions to view and/or manage datastore    entities
copeDatastore = "https://www.googleapis.com/auth/datastore"

// ScopeUserEmail grants permission to view the user's email address.
// It is required to access the datastore.
ScopeUserEmail = "https://www.googleapis.com/auth/userinfo.email"
)

type ehrEntity struct {
email       *datastore.Key
firstname   string
lastname    string
address     string
age         int8
dateofbirth time.Time
sex         bool
}

 func getCtx() *datastore.Client {
// Initialize an authorized transport with Google Developers Console
// JSON key. Read the google package examples to learn more about
// different authorization flows you can use.
// http://godoc.org/golang.org/x/oauth2/google
jsonKey, err := ioutil.ReadFile("filename.json")
opts, err := google.JWTConfigFromJSON(
    jsonKey,
    datastore.ScopeDatastore,
    datastore.ScopeUserEmail,
)
if err != nil {
    log.Fatal(err)
}

ctx := context.Background()
client, err := datastore.NewClient(ctx, "xxxx",     cloud.WithTokenSource(opts.TokenSource(ctx)))
if err != nil {
    log.Fatal(err)
}
// Use the context (see other examples)
return client
}

 func ExampleGet() {
ctx := context.Background()
client, err := datastore.NewClient(ctx, "xxxx")
if err != nil {
    log.Fatal(err)
}
key := datastore.NewKey(ctx, "User", "tluu@abc.com", 0, nil)
ehr := ehrEntity{
    nil,
    "tri",
    "luu",
    "addr1",
    20,
    time.Date(2009, time.January, 10, 23, 0, 0, 0, time.UTC),
    false}
if err := client.Get(ctx, key, ehr); err != nil {
    log.Fatal(err)
 }
 }

func main() {
getCtx()
fmt.Println("Pass authentication")
ExampleGet()
}

ctx := context.Background()
client, err := datastore.NewClient(ctx, "xxxx")
if err != nil {
    log.Fatal(err)
  }