AppSync event looks like a map and not like AppSyncResolverTemplate

Hello.

I'm awaiting events.AppSyncResolverTemplate having all usual fields like Operation, Version, Payload from AppSync.

My mapping template produced from the original *Invoke and forward arguments*

{
"version" : "2017-02-28",
"operation": "Invoke",
"payload": $util.toJson($context.arguments)
}

I thought I have to recieve a JSON with all those fields. But when I eventually decided to specify an event like an interface{} it turned out that I recieve a map[] of values

map[input:map[someField:1922 locationCountry:US]]

Can somebody clarify, please, if it works as expected or not?