===== Goroutine =====

==== What is it? ====
A goroutine is a lightweight thread managed by the Go runtime. You start it with the `go` keyword.

==== What is it used for? ====
  * Run tasks concurrently: I/O, API calls, background jobs.
  * Improve server throughput by doing work in parallel.

==== Example ====
<code go>
package main

import (
    "fmt"
    "time"
)

func work(name string) {
    fmt.Println("start:", name)
    time.Sleep(200 * time.Millisecond)
    fmt.Println("done:", name)
}

func main() {
    go work("A")
    go work("B")
    time.Sleep(500 * time.Millisecond) // demo: wait a bit
}
</code>

==== Important notes ====
  * Goroutines may stop when `main` exits.
  * In real code, use `sync.WaitGroup` or `context` to control lifecycle.

==== Hard words (English) ====
  * **lightweight** /ˈlaɪtweɪt/: nhẹ, ít tài nguyên
  * **thread** /θred/: luồng
  * **runtime** /ˈrʌntaɪm/: môi trường chạy
  * **concurrently** /kənˈkɝːəntli/: đồng thời
  * **throughput** /ˈθruːpʊt/: thông lượng
  * **lifecycle** /ˈlaɪfˌsaɪkəl/: vòng đời