title: JSON: Nesting a populated struct into a new struct
body: <p>I have a struct like so:</p>
  
  <pre><code>type my_struct struct {
    First  string `json:"first"`
    Second string `json:"second"`
    Number int    `json:"number"`
  }
  </code></pre>
  
  <p>When I marshal that into JSON, it outputs very simple JSON as you'd expect:</p>
  
  <pre><code>var output_json []byte
  output_json, _ = json.Marshal(output)
  fmt.Println(string(output_json))
  </code></pre>
  
  <p>Result:</p>
  
  <pre><code>{"first":"my_string","second":"another_string","number":2}
  </code></pre>
  
  <p>All fine so far!</p>
  
  <p>What I'd like to do, before marshalling that struct into JSON, is nest it inside another struct. The resulting output would be JSON that looks like this:</p>
  
  <pre><code>{
    "fields": {
      "first": "my_string",
      "number": 2,
      "second": "another_string"
    },
    "meta": "data"
  }
  </code></pre>
  
  <p>How can I do that?</p>