如何使用服务帐户为 Google Calendar API 设置 golang 客户端

Question

I've seen lots of documentation on Google API clients for users, but very little on using a service account. This isn't on behalf of a user, I'm just trying to get a client working with the Calendar APIs using a client ID and client secret, which would be provided via environment variables for me (I'd prefer to not read from a file).

Here's what I have so far:

package main

import (
  "context"

  clientCredentials "golang.org/x/oauth2/clientcredentials"
  google "golang.org/x/oauth2/google"
  calendar "google.golang.org/api/calendar/v3"
  apiOption "google.golang.org/api/option"
)

func main() {
  config := &clientCredentials.Config{
    ClientID:     "<my_id>",
    ClientSecret: "-----BEGIN PRIVATE KEY-----\n...",
    TokenURL:     google.Endpoint.TokenURL,
  }
  ctx := context.Background()
  client := config.Client(ctx)
  service, _ := calendar.NewService(ctx, apiOption.WithHTTPClient(client))
  
  calendarList, err := service.CalendarList.List().Do()
}

But I'm getting the following error:

Get "https://www.googleapis.com/calendar/v3/users/me/calendarList?alt=json&prettyPrint=false": oauth2: cannot fetch token: 400 Bad Request
Response: {
  "error": "unsupported_grant_type",
  "error_description": "Invalid grant_type: client_credentials"
}

Any help here is greatly appreciated, I'm new to Golang, Oauth2: and Google APIs :)

Answer 1

I believe your goal is as follows.

• You want to access Google Calendar using the service account with golang.

In this case, how about the following modification?

Modified script:

package main

import (
    "context"
    "fmt"

    calendar "google.golang.org/api/calendar/v3"
    "google.golang.org/api/option"
)

func main() {
    ctx := context.Background()
    v := `{"type": "service_account", "private_key": "-----BEGIN PRIVATE KEY-----\n###\n-----END PRIVATE KEY-----\n", "client_email": "###"}`
    service, _ := calendar.NewService(ctx, option.WithCredentialsJSON([]byte(v)))
    calendarList, _ := service.CalendarList.List().Do()
    fmt.Println(calendarList)
}

• If you want to use the file including the credential information, please modify it as follows.

   service, _:= calendar.NewService(ctx, option.WithCredentialsFile(credentialFile))

Note:

• If you want to retrieve the Google Calendar of your account, please share your Google Calendar with the email of the service account.

• Linda Lawton - DaImTo's comment: Google calendar doesn't support service account for standard google users. You need to configure domain wide delegation and impersonate a user on your google workspace account. and how to add the sub to this code. Google calendar doesn't support service account for standard google users. You need to configure domain wide delegation and impersonate a user on your google workspace account. and how to add the sub to this code.

  • References
    • https://developers.google.com/workspace/guides/create-credentials
    • https://pkg.go.dev/google.golang.org/api/impersonate#example-CredentialsTokenSource-ServiceAccount

References:

• calendar
• google-api-go-client