Parsing a date from a mongoDB with golang time.Now()

Question

I am creating a date using Go via time.Now() and it store it in the mongoDB with no issue. The date looks like 2023-02-28T20:10:46.140+00:00.

However when I try to retrieve it I get an error that reads:

{{"code":2, "message":"parsing time \"2023-02-28 20:10:46.14 +0000 UTC\" as \"2006-01-02T15:04:05Z07:00\": cannot parse \" 20:10:46.14 +0000 UTC\" as \"T\"", "details":[]}

It is coming from this piece of code.

createdAt, err := time.Parse(time.RFC3339, blog.CreatedAt.String())
if err != nil {
    return nil, err
}
updatedAt, err := time.Parse(time.RFC3339, blog.UpdatedAt.String())
if err != nil {
    return nil, err
}

tempBlog := &api.Blog{
    Id: blog.ID,
    CreatedAt: timestamppb.New(createdAt),
    UpdatedAt: timestamppb.New(updatedAt),

I found some useful documentation here and here and added the times parsed into Mongo manually, but I still run into this issue.

I have tried all of the time formats but it just results in a different error that is not able to parse.

Advice?

Answer 1

If you store time.Time MongoDB will auto retrieve it for you. The retrieved time is on UTC, if you want change to your local timezone, use time.Local().

package date_test

import (
    "context"
    "github.com/stretchr/testify/require"
    "go.mongodb.org/mongo-driver/bson"
    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
    "os"
    "testing"
    "time"
)

type Something struct {
    Name       string    `json:"name" bson:"name"`
    CreateTime time.Time `json:"createTime" bson:"createTime"`
}

func TestDate(t *testing.T) {
    raw := Something{Name: "demo", CreateTime: time.Now()}
    t.Logf("raw: %v", raw)
    ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
    defer cancel()
    client, err := mongo.Connect(ctx, options.Client().ApplyURI(os.Getenv("URI")))
    require.NoError(t, err)
    collection := client.Database("test").Collection("demo")
    _, err = collection.InsertOne(ctx, raw)
    require.NoError(t, err)
    var res Something
    err = collection.FindOne(ctx, bson.D{{"name", raw.Name}}).Decode(&res)
    require.NoError(t, err)
    t.Logf("res: %v", res)
    t.Logf("local time: %v", res.CreateTime.Local())
}

Run the test code it will print something like this

$ URI="mongodb://127.0.0.1:27017/" go test -v ./date_test.go
=== RUN   TestDate
    date_test.go:21: raw: {demo 2023-03-07 10:26:22.433473 +0800 CST m=+0.009080292}
    date_test.go:32: res: {demo 2023-03-07 02:26:22.433 +0000 UTC}
    date_test.go:33: local time: 2023-03-07 10:26:22.433 +0800 CST
--- PASS: TestDate (0.01s)
PASS
ok      command-line-arguments  0.912s

the mongo store the time like this

> db.demo.find().pretty()
{
    "_id" : ObjectId("6406a0ce4cfff0411ca8d98b"),
    "name" : "demo",
    "createTime" : ISODate("2023-03-07T02:26:22.433Z")
}

source code is here https://gist.github.com/alex-x-crypto/14c15d4921f1ece2962302cce87c97a8