title: Creating a Proper avro schema for timestamp record
body: <p>I would like to know what the proper avro schema would be for some json to avro conversion that is in this format:</p>
  
  <pre><code>{"entryDate": "2018-01-26T12:00:40.930"}
  </code></pre>
  
  <p>My schema:</p>
  
  <pre><code>{
      "type" : "record",
      "name" : "schema",
      "fields" : [{
          "name" : "entryDate",
          "type" : ["null", {
              "type" : "long",
              "logicalType" : "timestamp-micros"
          }],
          "default" : null
      }]
  }
  </code></pre>
  
  <p>I keep getting </p>
  
  <pre><code>`'Cannot convert field entryDate: Cannot resolve union: 
  "2018-01-26T12:00:40.930" 
  not in 
  ["null",{"type":"long","logicalType":"timestamp-millis"}]'`
  </code></pre>