title: Why can't I use the blank identifier in the following Go code?
body: <pre><code>for _, arg := range flag.Args() {
      go func() {
          path.Walk(arg, dupes, walkerrs)
          walkend &lt;- true
      }()
  }
  for _ := range flag.Args() {
      if !&lt;-walkend {
          os.Exit(1)
      }
  }
  </code></pre>
  
  <p>The second use of <code>_</code> gives this error: <code>no new variables on left side of :=</code>. What have I done wrong?</p>