Settings > More settings > Applications > Autostart > enable Swoo
Swipe up in your home screen while the app is open in background, and swipe the app icon down > tap the lock icon
Settings > Battery > Background power consumption > Swoo > High background power usage
Using iManager:
i Manager > App manager > Autostart manager > enable Swoo
i Manager > Settings icon > Speedup whitelist > turn on the switch to add Swoo
i Manager > Power manager > Excessive background battery usage > Swoo > High background power usage