Getting null while parsing JSON using jq in shell script

Question

I'm parsing below JSON using jq in my shell script, but I'm getting null while parsing this field config.subtype. And I want to check if config.subtype value is mobile, I want to update the value as 1000 for this field config.price and print the complete JSON. What I'm doing wrong here and how to update the existing JSON field value.

Appreciated your help in advance! Thanks!

Please find my code below:

test.json

{
    "name": "myapp",
    "product": {
        "config.type": "electronics",
        "config.count": "5",
        "config.subtype": "mobile",
        "config.price": ""
    }
}

test.sh

#!/bin/bash
#

    result=$(cat test.json| jq '.product.config.type')
    echo $result