Step 1: Go to Settings, either from the app drawer or from the notification panel.
Step 2: Tap "Battery" from the Settings list and then click on "Battery optimization" option from the top-right menu icon.
Step 3: Select "All apps" from the options to bring the list of all the apps on which doze mode is enabled.
Step 4: Choose Skooly app to disable doze mode.
Step 5: Tap "Don't optimize" and then click "Done".