Token from Google Credentials Service Account NULL - google-oauth

Question

I am attempting to retrieve the credentials for my Google service account with the following code:
package function
import com.amazonaws.services.lambda.runtime.Context
import com.amazonaws.services.lambda.runtime.LambdaLogger
import com.amazonaws.services.lambda.runtime.RequestHandler
import pojo.Request
import com.google.api.client.googleapis.auth.oauth2.GoogleCredential
import com.google.api.services.sqladmin.SQLAdminScopes
import pojo.Response
class GoogleAuth implements RequestHandler<Request, Response> {
private LambdaLogger logger
#Override
Response handleRequest(Request input, Context context) {
logger = context.getLogger()
ClassLoader classLoader = getClass().getClassLoader()
File jsonCredentials = new File(classLoader.getResource("leads-cloud-function-service-account.json").getFile())
FileInputStream fis = new FileInputStream(jsonCredentials)
GoogleCredential credential = GoogleCredential.fromStream(fis).createScoped(Collections.singleton(SQLAdminScopes.SQLSERVICE_ADMIN))
credential.getClientAuthentication()
println("Thai test" + credential.getExpirationTimeMilliseconds())
print("This is the credential" + credential.getAccessToken())
return (new Response())
}
}
The information about the milliseconds for expiration and the AccessToken are null. Has anyone ever experienced this?

Answer 1

So I have resolved this myself by adding before the getToken the following command:
credential.refreshToken()
This is not properly documented in google's website but after adding it, this worked perfectly and the results are displayed with actual values.
Some other error I faced was the "com.google.common.io.ByteStreams.exhaust(Ljava/io/InputStream;)J", in order to resolve it I had to correct the dependency I was using to this one:
<dependency>
<groupId>com.google.api-client</groupId>
<artifactId>google-api-client</artifactId>
<version>1.31.1</version>
</dependency>
so, keep on mind that too!