title: How can I prevent a type being used as a map key?
body: <p>I have a type that can be used as a map key, but I want to prevent this from occurring. I assumed that if the type contained a private member it wouldn't be possible from other packages, but this appears to work anyway. What's the best way to make the type unusable as a map key?</p>
  
  <pre><code>type MyType struct {
      A *A
      b b
  
      preventUseAsKey ?
  }
  </code></pre>