I have already defined a custom network security config and included it in my manifest as recommended here
res/xml/network_security_config.xml:
Create a XML res/xml/network_security_config.xml
<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
<base-config cleartextTrafficPermitted="true" />
</network-security-config>
Reference this file in your tag Application, inside AndroidManifest.xml. Like:
android:networkSecurityConfig="@xml/network_security_config"
Replace the BASE_URL protocol from http://... to https://