title: Find by id with mgo
body: <p>I would like to find a data by <code>_id</code>. I know that this data exists and that this <code>_id</code> exist (I've tested it with pymongo).</p>
  
  <p>But the code below doesn't find it:</p>
  
  <pre><code>type id_cookie struct {
      IdCookie int
  }
  
  func get_id_mongo() int {
      session, err := mgo.Dial("127.0.0.1")
      if err != nil {
          panic(err)
      }
      defer session.Close()
  
      // Optional. Switch the session to a monotonic behavior.
      session.SetMode(mgo.Monotonic, true)
  
      c := session.DB("id_bag").C("id_cookie")
      data := id_cookie{}
      err2 := c.FindId(bson.M{"_id": bson.ObjectIdHex("58593d1d6aace357b32bb3a1")}).One(&amp;data)
      if (err2 != nil){
          Info.Println("error")
          Info.Println(err2)
      }
      Info.Println(data)
      return data.IdCookie
  }
  </code></pre>
  
  <p>It just returns me a <code>0</code>.</p>
  
  <p>But I can find it using pytmongo and python.</p>
  
  <pre><code>import requests
  import pymongo 
  from pymongo import MongoClient
  from bson.objectid import ObjectId
  from pprint import pprint
  client = MongoClient('127.0.0.1', 27017)
  
  import base64
  
  
  
  db = client.id_bag
  pprint(db.collection_names())
  result = db.id_cookie.insert_one(
      { 'IdCookie': 1
      })
  print(result.inserted_id)
  
  data = db.id_cookie.find_one({"_id": ObjectId("58593d1d6aace357b32bb3a1")})
  print(data)
  </code></pre>
  
  <p>here are the result :</p>
  
  <pre><code>['id_cookie', 'system.indexes']
  58593d2d6aace357b32bb3a3
  {'IdCookie': 1, '_id': ObjectId('58593d1d6aace357b32bb3a1')}
  </code></pre>
  
  <p>Does anyone have any idea?</p>
  
  <p>Edit :
  i've try with :</p>
  
  <pre><code>err2 := c.FindId(bson.ObjectIdHex("58593d1d6aace357b32bb3a1")).One(&amp;data)
  </code></pre>
  
  <p>but i still have 0 :</p>
  
  <pre><code>INFO: 2016/12/20 15:42:08 Cookie_Id.go:147: 1
  INFO: 2016/12/20 15:42:08 Cookie_Id.go:149: 2
  INFO: 2016/12/20 15:42:18 Cookie_Id.go:87: data
  INFO: 2016/12/20 15:42:18 Cookie_Id.go:88: {0}
  INFO: 2016/12/20 15:42:18 Cookie_Id.go:89: 0
  INFO: 2016/12/20 15:42:18 Cookie_Id.go:118: 0
  INFO: 2016/12/20 15:42:18 Cookie_Id.go:128: OK
  </code></pre>