How Can I Add a 'count' Key to a JSON String with an Unknown Structure?

Decoding JSON with an Unknown Structure

The question arises when attempting to modify a JSON string of an unknown structure. The objective is to add a "count" key to the existing JSON:

Original JSON:

{ "votes": { "option_A": "3" } }

Desired JSON:

{ "votes": { "option_A": "3" }, "count": "1" }

The challenge lies in the variability of the JSON structure, making it impractical to use a conventional JSON decoder with a predetermine structure.

Solution: Unmarshal into a Map

To overcome this challenge, a practical approach is to unmarshal the JSON into a map of strings to interfaces:

var raw map[string]interface{}
json.Unmarshal(in, &raw)

This allows for the manipulation of the JSON data on a key-value basis. In this case, a new "count" key can be added:

raw["count"] = 1

To generate the desired JSON string, the modified map is remarshaled into a JSON string:

out, err := json.Marshal(raw)

As a result, the unknown JSON structure can be modified and the "count" key can be added as desired.

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