title: How to check the uniqueness inside a for-loop?
body: <p>Is there a way to check slices/maps for the presence of a value?</p>
  <p>I would like to add a value to a slice <em><strong>only</strong></em> if it does <em><strong>not</strong></em> exist in the slice.</p>
  <p>This works, but it seems verbose. Is there a better way to do this?</p>
  <pre><code>orgSlice := []int{1, 2, 3}
  newSlice := []int{}
  newInt := 2
      
  newSlice = append(newSlice, newInt)
  for _, v := range orgSlice {
      if v != newInt {
          newSlice = append(newSlice, v)
      }
  }
  
  newSlice == [2 1 3]
  </code></pre>