Tell us about the types of contexts in Go: Background, WithTimeout, WithCancel, and others.

The Go package context is used for managing the lifetime of requests, canceling operations, and passing values between goroutines.

Main types of contexts:

• context.Background() — a base, empty context, usually used as the root context in an application.
• context.TODO() — a temporary context when it is not yet determined which one to use.
• context.WithCancel(parent) — creates a new context that can be canceled manually by calling the cancel() function. Cancellation propagates to all child contexts.
• context.WithTimeout(parent, duration) — creates a context that automatically cancels after a specified timeout.
• context.WithDeadline(parent, time) — similar to WithTimeout, but with a specific date and time for expiration.
• context.WithValue(parent, key, value) — creates a context with an attached value, which can be retrieved in child contexts.

Example of usage with timeout and cancellation:

ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
defer cancel()

select {
case <-time.After(3 * time.Second):
    fmt.Println("operation completed")
case <-ctx.Done():
    fmt.Println("operation cancelled or timed out")
}

Thus, contexts allow controlling the lifetime of operations, canceling them, and passing data between goroutines, which is especially important for network requests and long computations.