type User struct {
	bongo.DocumentBase `bson:",inline"`
	UserName     string `example:"wxf"`
	Password string `json:"-" example:"111111"  bson:",omitempty"`
	Phone string ` bson:",omitempty"`
	Email string ` bson:",omitempty"`
}
u:=new(User)
err:=bgoUser.FindOne(bson.M{"username":uname},u)  

err:=bgoUser.FindOne(User{UserName:uname},u)  // if DocumentBase fields  bson omitempty;  then this line will work too.