Parse MongoDB results Using Go and mgo

Question

I am trying to parse the results of a MongoDB query from Go. I have document(s) that output from my Database as a result of:

db.getCollection('People').find({})

{
    "_id" : ObjectId("5730fd75113c8b08703b5974"),
    "firstName" : "George",
    "lastName" : "FakeLastName"
}
{
    "_id" : ObjectId("5730fd75113c8b08703b5975"),
    "firstName" : "John",
    "lastName" : "Doe"
}
{
    "_id" : ObjectId("5730fd75113c8b08703b5976"),
    "firstName" : "Jane",
    "lastName" : "Doe"
}

Here is the Go code that I am trying to use:

package main

import (
    "fmt"
    "log"
    "gopkg.in/mgo.v2"
)

type Person struct {
    FirstName string `bson: "firstName" json: "firstName"`
    LastName string `bson: "lastName json: "lastName"`
}

func main() {
    session, err := mgo.Dial("10.0.0.89")
    if err != nil {
            panic(err)
    }
    defer session.Close()

    // Optional. Switch the session to a monotonic behavior.
    session.SetMode(mgo.Monotonic, true)

    c := session.DB("PeopleDatabase").C("People")

    var people []Person
    err = c.Find(nil).All(&people)
    if err != nil {
            log.Fatal(err)
    }

    for _, res := range people{
        fmt.Printf("Name: %v\n", res)
    }
}

When I run this code I get the following Output:

Name: { }
Name: { }
Name: { }

When using res.FirstName in place of res I just get a space in lieu of the {}.

I have been over the documentation in the following locations:

https://labix.org/mgo

https://godoc.org/gopkg.in/mgo.v2#Collection.Find

https://gist.github.com/border/3489566

I would be extemely grateful for any help that can be given. Thank You.

Answer 1

Remove the space in the middle of tags.

Use bson:"firstName" instead of bson: "firstName"

type Person struct {
    FirstName string `bson:"firstName" json:"firstName"`
    LastName string `bson:"lastName json:"lastName"`
}

From documentation at https://golang.org/pkg/reflect/#StructTag ,

By convention, tag strings are a concatenation of optionally space-separated key:"value" pairs.

So there should be no space between key and value. Different pairs of a key and a value could be separated by a space.