Go Struct Tags: Marshaling and Unmarshaling JSON Data

Struct tags in Go provide a powerful mechanism for associating metadata with struct fields. This metadata can be used by libraries to control behavior, such as how data is marshaled and unmarshaled into different formats. In this challenge, you'll leverage struct tags to customize JSON encoding and decoding for a User struct.

Problem Description

Your task is to create a User struct with fields for ID, Username, Email, and IsActive. You need to use Go struct tags to specify how these fields should be represented when marshaling to and unmarshaling from JSON.

Specifically:

• The ID field should be represented as "user_id" in JSON.
• The Username field should be represented as "name" in JSON.
• The Email field should be represented as "email_address" in JSON.
• The IsActive field should be represented as "active" in JSON.
• You should also handle the case where a JSON field might be missing or empty.

You will need to use the encoding/json package to perform the marshaling and unmarshaling operations.

Examples

Example 1:

Input Struct:
User{ID: 1, Username: "alice", Email: "alice@example.com", IsActive: true}

JSON Output:
{"user_id":1,"name":"alice","email_address":"alice@example.com","active":true}

Explanation: The struct fields are marshaled into JSON according to their respective struct tags.

Example 2:

Input JSON:
{"user_id": 2, "name": "bob", "email_address": "bob@example.com"}

Output Struct:
User{ID: 2, Username: "bob", Email: "bob@example.com", IsActive: false}

Explanation: The JSON fields are unmarshaled into the struct. Since "active" is missing in the JSON, the `IsActive` field defaults to its zero value (false for boolean).

Example 3:

Input JSON:
{"user_id": 3, "active": true}

Output Struct:
User{ID: 3, Username: "", Email: "", IsActive: true}

Explanation: Fields like "name" and "email_address" are missing in the JSON, so their corresponding struct fields will receive their zero values ("" for strings). The "active" field is present and correctly unmarshaled.

Constraints

• The ID field will always be an integer.
• The Username, Email fields will always be strings.
• The IsActive field will always be a boolean.
• The input JSON will conform to valid JSON syntax.
• There are no strict performance constraints for this challenge.

Notes

• The encoding/json package in Go is your primary tool.
• Pay close attention to the syntax for defining struct tags in Go.
• Consider how the encoding/json package handles missing fields during unmarshaling.
• You will be implementing marshaling (struct to JSON) and unmarshaling (JSON to struct).