title: json tag without starting double quote worked
body: <p>I have a struct with json tags. One of then was without starting double quote. During the testing it did work. I wonder why and is there a tool to catch such typos?</p>
  
  <pre><code>type req struct {
      Name        string `json:name"`
  }
  </code></pre>
  
  <p>I am on <code>go1.13 linux/amd64</code>.</p>