Bson interface has some problems - mongodb

Question

I uesd MongoDB v3.6.4 with mgo(gopkg.in/mgo.v2) package
Bson
var id interface{}
id = 249678041972736
bson.M{"_id": id}
var id int64
id = 249678041972736
bson.M{"_id": id}
Tow bsons are not same?
eg:
func GetUser(id interface{}) (*User, error) {
session := MongoDB()
defer session.Close()
var m *User
err := session.DB.C("user").Find(&bson.M{"_id": id}).One(&m)
// ！！！err: not found
if err != nil {
return nil, err
} else {
return m, nil
}
}
but:
func GetUser(id int64) (*User, error) {
session := MongoDB()
defer session.Close()
var m *User
err := session.DB.C("user").Find(&bson.M{"_id": id}).One(&m)
// !!! err == nil
if err != nil {
return nil, err
} else {
return m, nil
}
}
GetUser(id interface{}) can get err (not found)
GetUser(id int64) can get nil err
Pay attention to error
I used function GetUser and import same value 249678041972736
but different parameter type get different result
Why?

Answer 1

You are putting an unnecessary & in front of the bson.M{…
err := session.DB.C("user").Find(bson.M{"_id": id}).One(&m)
The use of bson.M in the find is also unnecessary, mgo has a call of FindId specifically for the search you are doing.
err := session.DB.C("user").FindId(id).One(&m)
gopkg.in/mgo.v2 is now marked as unmaintained. github.com/globalsign/mgo and github.com/globalsign/mgo/bson are the two maintained forked libraries. I have found no problems using them instead pf gopkg.in