What is the difference between Goroutines and threads in Go, and when to use each of them?

Goroutines and threads are both mechanisms for implementing concurrency in a program, but they differ in several ways.

Goroutines are lightweight, user-space threads managed by the Go runtime, while threads are managed by the operating system kernel. Goroutines are cheaper to create and switch between than threads, so it's common to use many of them in a single program. On the other hand, threads are more expensive to create and switch between, so it's typically better to use fewer of them.

Goroutines also have built-in support for communication and synchronization through channels, which can be used to pass data between Goroutines or coordinate their activities. This makes it easier to write correct concurrent code in Go, as channels provide a safe and easy-to-use way to manage shared state.

Threads, on the other hand, typically use locks and other synchronization primitives to manage shared state. This can be more error-prone and harder to reason about than using channels, especially for larger programs with many concurrent threads.

In general, it's a good idea to use Goroutines and channels for most concurrent tasks in Go, reserving the use of threads for cases where you need to interact with low-level system APIs or when you need more fine-grained control over thread scheduling.