Parsing arbitrary JSON documents

Parsing into a struct is very convenient but sometimes you don’t know the structure of JSON document upfront.

For arbitrary JSON documents we can decode into a map[string]interface{}, which can represent all valid JSON documents.

For basic JSON types, the value in the map is bool, int, float64 or string.

For JSON arrays, the value is []interface{}.

For JSON dictionaries, the value is (again) map[string]interface{}.

This approach is flexible but dealing with map[string]interface{} to access values is rather painful.