title: How to marshal json string to bson document for writing to MongoDB?
body: <p>What I am looking is equivalent of <a href="https://api.mongodb.com/java/3.2/org/bson/Document.html#parse-java.lang.String-" rel="noreferrer">Document.parse()</a></p>
  
  <p>in golang, that allows me create bson from json directly? I do not want to create intermediate Go structs for marshaling</p>