如何在Golang Google数据存储包中正确使用上下文？

Question

I've started using Google Cloud Datastore in one of the project in the company I currently work in.

https://godoc.org/cloud.google.com/go/datastore

In the provided example, they use a context and pass it to the connection instance

ctx := context.Background()
dsClient, err := datastore.NewClient(ctx, "my-project")

Through the documentation you will see that they pass a context to all the functions that makes operations on the database, I am not sure if they are passing the same pointer or create a new pointer for each operation.

The current setup that I have is a global variable for the context in a package called "store" which I keep all the structs functions that communicate with the db, and I use that global variable each time. I don't know what is the effect of that, I am not sure why the context is used, Should I get reference of context.Background() each time I make operations on the database ?

Answer 1

context.Background is the global context--so no need for you global variable. Most of the time you'll want to use a child of that context, with a cancel or a timeout.

ctx, cancel := context.WithCancel(context.Background)
//or
ctx, cancel := context.WithTimeout(context.Background, time.Second * 30) 

Then you can use the cancel function to close down your application nicely, or cancel and retry if a request is hanging. If you never plan on canceling or timing out operations, then using context.Background is fine.

Also context.Context is an interface so it's always passed by reference, so all uses of a certain instance point to the same context.