title: Golang dynamically creating member of struct
body: <p>I know there is struct in Go, but for all I know, you have to define struct </p>
  
  <pre><code>type Circle struct{
      x,y,r float64
  }
  </code></pre>
  
  <p>I am wondering how you can declare a new variable that doesn't exist in the struct</p>
  
  <pre><code>circle := new(Circle)
  circle.color = "black"
  </code></pre>