title: Using `json:",string"` returning invalid use of ,string struct tag, trying to unmarshal unquoted value
body: <p>When trying to parse a json with a float value for distance to the following struct</p>
  
  <pre><code>type CreateBookingRequest struct {
      Distance          float64           `json:"distance,string"`
      DistanceSource    string            `json:"distanceSource"`
  }
  </code></pre>
  
  <p>I get the following error</p>
  
  <blockquote>
    <p>json: invalid use of ,string struct tag, trying to unmarshal unquoted
    value into [34 100 105 115 116 97 110 99 101 34]%!(EXTRA
    *reflect.rtype=dto.CreateBookingRequest)</p>
  </blockquote>
  
  <p>Is there a way for me to avoid the error/get a better error message? </p>
  
  <p><strong>Edit:</strong>
  I am actually expecting the users of the API to pass in a string value but if they for some reason pass in a non-string value, I would like to be able to tell them clearly, instead of this hard to read error message. </p>