title: Which package contains merge function in golang
body: <p>I am trying to merge 2 channels in an iteration so that I can retrieve both channels values for each step.
  I wrote the following lines</p>
  
  <pre><code>ch1, ch2 := make(chan int), make(chan int)
  go Walk(t1, ch1)
  go Walk(t2, ch2)
  
  for ints := range merge(ch1, ch2) {
      fmt.Println(ints)
  }
  </code></pre>
  
  <p>but when I run it, I get "prog.go:31: undefined: merge".
  I would like to know where this merge function is located.</p>