strict json parser in golang

In Go, I have some JSON from third-party API and then I'm trying to parse it:

b := []byte(`{"age":21,"married":true}`)
var response_hash map[string]string
_ = json.Unmarshal(b, &response_hash)

But it fails (response_hash becomes empty) and Unmarshal can handle only JSON with quotes:

b := []byte(`{"age":"21","married":"true"}`)
var response_hash map[string]string
_ = json.Unmarshal(b, &response_hash)

Is there any way to read the first version of JSON from third-party API?