DefaultTaskContainer#NamedDomainObjectProvider.configure(Action) on task set cannot be executed in the current context

Google broke something in com.google.gms:google-services:4.3.9

Change it to com.google.gms:google-services:4.3.8 and I suspect it will work. I have the same issue, and no amount of fiddling around with gradle scripts has fixed it, only downgrading.

A new version 4.3.10 was released with a fix. Give it a try

https://firebase.google.com/support/release-notes/android#google-services_plugin_v4-3-10

Use classpath 'com.google.gms:google-services:4.3.10' in build.gradle(project: app_name)

It will be fixed.