In its simpliest form, context is an interface

from the Go docs

     Package context defines the Context type, which carries deadlines, cancellation signals, and other request-scoped values across API boundaries and between processes.

This may seem confusing but in essense context serves two purposes within a Go application

1. Timeouts
2. Storing values

In general to craete a context you will call the context.Background() function. when you are unsure of what context to use you will use context.TODO() function

Timeouts

func main() {
    ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
    defer cancel()

    val, err := doSomething(ctx)
    ...
}

In this example we are creating a context with a timeout of 1 second, this means that if the function doSomething does not return within 1 second the context will be canceled.

Storing Values

func main() {
    ctx := context.WithValue(context.Background(), "key", "value")
    val := ctx.Value("key")
    val, err := doSomething(ctx)
    ...
}

In this example we are creating a context with a value of “key” and “value”. We can then access this value later in our code by calling ctx.Value("key"), for example:

func doSomething(ctx context.Context) (string, error) {
    val := ctx.Value("key").(string)
    // do something with val    
    ...
}

Conclusion

Context is a powerful tool in Go, it is used to pass values and timeouts between functions. It is used in many places in the Go standard library, such as the net/http package and the database/sql package. Have fun using it!