@codyoss can you please check this or mention someone who can confirm this bug or [recommend any solution?
thanks :)

Hey @taalhach sorry you are having problems with authentication. My best guess is that you are pointing to a service account key that is no long active on your project. I tried to reproduce this with the sample code given and it work for me when I pointed to a valid service account with the correct permissions.

@codyoss as you can see from screenshot it says it is an active key and i have generated more keys and tried with those but no luck.

opt := option.WithCredentialsFile("path/to/key-fa7a66f98203.json")

c, err := documentai.NewDocumentProcessorClient(ctx, opt)

does it have anything to do with gcp cli as i haven't installed it because client libraries can take care of auth by themselves ?

@codyoss or is there something wrong with my service account setup as i have created using instructions here

finally after searching and spending a lot of time i found that was an issue of scopes when we pass credentials via file we need to add an extra option.ClientOption which specifies the scopes for oauth2 access token. as we use service account so need to pass IAM API scope. unfortunately documentation does not even have any clue about that, i hope it can be of some help for someone. hit upvote here at slackoverflow which really helped me.
final piece of code:

		req := &documentaipb.ProcessRequest{
			Source: &documentaipb.ProcessRequest_RawDocument{
				RawDocument: &documentaipb.RawDocument{
					Content:  bytes,
					MimeType: "application/pdf",
				},
			},
			Name: "projects/{PROJECT_ID}/locations/us/processors/{PROCESSOR_ID}",
		}

		opt := option.WithCredentialsFile("path/to/credentials/file.json")
		ctx := context.Background()
                scopes := documentai.DefaultAuthScopes()
		c, err := documentai.NewDocumentProcessorClient(ctx, opt, option.WithScopes(scopes...))
		if err != nil {
			log.Debugf("failed to create client, err: %v", err)
			os.Exit(0)
		}
		defer c.Close()

		resp, err := c.ProcessDocument(ctx, req)
		if err != nil {
			log.Debugf("failed to process document, err: %v", err)
			os.Exit(0)
		}

@taalhach Thanks for reporting back. I am still not able to reproduce this issue, but I am glad you got your code working. Default scopes should be added to the client for you unless you override them. The scope you are manually passing here looks to be the scope add be default. 1 2

@codyoss thanks for simplifying this piece of code really appreciate that :)