title: detect duplicate in JSON String Golang
body: <p>I have JSON string like </p>
  
  <pre><code>"{\"a\": \"b\", \"a\":true,\"c\":[\"field_3 string 1\",\"field3 string2\"]}"
  </code></pre>
  
  <p>how to detect the duplicate attribute in this json string using Golang</p>