DriveClient and DriveResourceClient always throwing FATAL EXCEPTION - google-drive-api

Question

I got a successful GoogleSignInAccount object, and I need to get both DriveClient and DriveResourceClient of this account, I'm actualy doing in this way:
GoogleSignInAccount account = GoogleSignIn.getLastSignedInAccount(this);
if(account != null){
DriveClient driveClient = Drive.getDriveClient(this,account);
DriveResourceClient driveResourceClient = Drive.getDriveResourceClient(this,account);
}
But, when I try to perform simple tasks like:
DriveFolder root = driveResourceClient.getRootFolder().getResult();
I get this error:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.myorg.myapp, PID: 21980
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myorg.myapp/com.myorg.myapp.DriveUpload2}: java.lang.IllegalStateException: Task is not yet complete
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.access$900(ActivityThread.java:150)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.IllegalStateException: Task is not yet complete
at com.google.android.gms.common.internal.Preconditions.checkState(Unknown Source)
at com.google.android.gms.tasks.zzu.zzb(Unknown Source)
at com.google.android.gms.tasks.zzu.getResult(Unknown Source)
at com.myorg.myapp.DriveUpload2.signIn(DriveUpload2.java:94)
at com.myorg.myapp.DriveUpload2.onCreate(DriveUpload2.java:139)
at android.app.Activity.performCreate(Activity.java:6406)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
at android.app.ActivityThread.access$900(ActivityThread.java:150) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5417) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
All scope configurations on Google Console Credentials page are correct, and required scope like Drive.SCOPE_FILE and Drive.SCOPE_APPFOLDER have already been requested during the creation of GoogleSignInOptions.