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package argvpb
import (
"fmt"
"time"
)
// RunIfTakesLonger schedules a function `f` to run after a duration `d`.
// It returns a "cancel" function. If the cancel function is called before
// the duration `d` has passed, the scheduled function `f` will not be executed.
//
// This is designed to be used with defer, like so:
//
// func myFunc() {
// cancel := RunIfTakesLonger(time.Second, func() {
// fmt.Println("myFunc took more than a second!")
// })
// defer cancel()
//
// // ... rest of the function
// }
func RunIfTakesLonger(d time.Duration, f func()) (cancel func()) {
// time.AfterFunc executes a function in its own goroutine after the
// specified duration. It returns a Timer that can be used to cancel it.
timer := time.AfterFunc(d, f)
// We return a function that stops the timer.
// The caller is expected to call this function using `defer`.
return func() {
// The Stop method returns true if it successfully prevented the
// timer from firing. We don't need the return value here, but it's
// useful for understanding.
timer.Stop()
}
}
// A task that takes less time than the timeout.
func shortTask() {
fmt.Println("--- Running shortTask (will take 500ms) ---")
cancel := RunIfTakesLonger(time.Second, func() {
fmt.Println("!!! This should NOT be printed !!!")
})
defer cancel()
fmt.Println("shortTask: working...")
time.Sleep(500 * time.Millisecond)
fmt.Println("shortTask: finished.")
}
// A task that takes more time than the timeout.
func longTask() {
fmt.Println("\n--- Running longTask (will take 2 seconds) ---")
cancel := RunIfTakesLonger(time.Second, func() {
fmt.Println(">>> longTask took more than 1 second! Clean-up function executed. <<<")
})
defer cancel()
fmt.Println("longTask: working...")
time.Sleep(2 * time.Second)
fmt.Println("longTask: finished.")
}
func main() {
shortTask()
longTask()
}
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