title: How to take STDIN in Swift playground
body: <p>I know that to program in STDIN and STDOUT, we need to make an command line project in Xcode. 
  But how do I take a standard input in playground. </p>
  
  <p>Whenever I try to run such code in playground</p>
  
  <pre><code>var input = readLine()!
  </code></pre>
  
  <p>I always get this error</p>
  
  <blockquote>
    <p>Execution was interrupted, reason: EXC_BAD_INSTRUCTION
    (Code=EXC_l386_INVOP, subcode=0x0)</p>
  </blockquote>
  
  <p>Is it possible to take STDIN in playground or not?</p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>I know this error is because of <strong>nil</strong> <code>input</code> variable but want to know how to overcome this nil value.</p>