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I have a standard mongo db connection that is initialised using the official Go driver (mongo-go-driver)

The context for this db connection and the connection details are:

setContext = context.Background()

mongoURI := fmt.Sprintf("mongodb://%s:%s@%s/?authSource=admin", mongoUser, mongoPwd, mongoAddress)

mongoContext, cancel := context.WithTimeout(setContext, 5*time.Second)

clientOptions := options.Client().ApplyURI(mongoURI).SetMaxPoolSize(50)

defer cancel()

mongoSession, err := mongo.Connect(mongoContext, clientOptions)

From the documentation, https://godoc.org/golang.org/x/net/context I understand that this is correct:

Background returns a non-nil, empty Context. It is never canceled, has no values, and has no deadline. It is typically used by the main function, initialization, and tests, and as the top-level Context for incoming requests.

Now, when running my queries against this connection, what context should I be using?

Here's an example of using the connection:

mongoConnection := myMongoSessionOfficialDriver.Database(db).Collection(collection)

pipeOptions := options.Aggregate().SetMaxTime(time.Second * 10)

mongoCursor, err := mongoConnection.Aggregate(context.TODO(), aggregationPipeline, pipeOptions)

My question is this: what should the context be for the cursor?! Should it be background() i'm thinking not if it should be cancelled (when my query returns the data)

In the documentation, for TODO() it says:

TODO returns a non-nil, empty Context. Code should use context.TODO when it's unclear which Context to use or it is not yet available (because the surrounding function has not yet been extended to accept a Context parameter). TODO is recognized by static analysis tools that determine whether Contexts are propagated correctly in a program.

Okay... well what context should I be using for aggregate queries?

SuperSecretAndNotSafeFromWork
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    `Background` and `TODO` are exactly the same, and neither do anything special. – JimB May 02 '19 at 16:41
  • Hmmm how do you know that? That isn't clear from the context documentation. Also, do you know if I should even be using the background/TODO context in my... context? – SuperSecretAndNotSafeFromWork May 02 '19 at 16:59
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    Besides that the documentations states it, you can look at the source: https://golang.org/src/context/context.go#L197. You need _a_ context, so you have to start somewhere. If you don't have a context, the only root contexts are from `Background` or `TODO`. – JimB May 02 '19 at 17:06
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    `TODO` is intended as a placeholder for cases where you later intend to pass a "real" context but you don't have one to use yet. If you just need a context with no intention of cancelling, use `Background`. That's a purely semantic difference though, they have no functional difference. – Adrian May 02 '19 at 17:55
  • Thanks for the explanation with these, what context would you recommend for the aggregate queries though? The context should be cancelled when the read operation is completed – SuperSecretAndNotSafeFromWork May 03 '19 at 09:11
  • Follow what the documentation says. If you're planning on threading in a parent context in the future, and want to look for calls to `context.TODO`, then use it. If you're not, then don't use it. – JimB May 03 '19 at 13:07

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