How is the execution of a goroutine related to CPU threads, and how is it assigned to a specific thread?

In Go, goroutines are lightweight threads managed by the Go runtime, not directly by the operating system. They are launched within OS threads, but Go uses its own scheduler, which distributes many goroutines across a limited number of threads (M — OS threads).

The assignment of a goroutine to a thread occurs through an M:N model, where M is the number of OS threads, and N is the number of goroutines. The Go scheduler dynamically switches the execution of goroutines between threads to efficiently utilize CPU resources.

Thus, a goroutine is not bound to a specific processor thread, and the Go scheduler decides which thread and when it will run. This allows thousands of goroutines to run with minimal overhead compared to OS threads.

Example:

func main() {
    go func() {
        fmt.Println("Goroutine is running")
    }()
    time.Sleep(time.Second)
}

Here, the goroutine is launched, and the Go scheduler assigns its execution to one of the available OS threads.