What is a goroutine? How is it structured?

A goroutine is a lightweight thread of execution in the Go language. Unlike system threads, goroutines are managed by the Go runtime and have a very small stack (starting from a few kilobytes and can grow dynamically). This allows hundreds of thousands of goroutines to run concurrently with low overhead.

Goroutine structure:

• When creating a goroutine (using the go operator), the Go scheduler places it in a queue of ready-to-run tasks.
• The Go runtime uses M:N scheduling: M system threads (OS threads) serve N goroutines.
• Goroutines switch at the runtime level, which is faster than switching system threads.
• Each thread (M) can execute multiple goroutines (N), switching between them when blocked or as needed.

Example of creating a goroutine:

func sayHello() {
    fmt.Println("Hello from goroutine")
}

func main() {
    go sayHello() // start a goroutine
    time.Sleep(time.Second) // wait for the goroutine to finish
}