title: What is the zero for string?
body: <pre><code>func NewKey(c appengine.Context, kind, stringID string, intID int64, parent *Key) *Key
  </code></pre>
  
  <p>The documentation says :</p>
  
  <blockquote>
    <p>NewKey creates a new key. kind cannot be empty. Either one or both of
    stringID and intID must be <strong>zero</strong>. If both are zero, the key
    returned is incomplete. parent must either be a complete key or nil.</p>
  </blockquote>
  
  <p>What is the zero for string?</p>
  
  <p>I tried <code>0</code> and <code>nil</code>, and I got errors like:</p>
  
  <pre><code>cannot use nil as type string in function argument
  </code></pre>