How to implement a concurrent timer using channels and sync in Golang?

To implement a concurrent timer using channels and sync in Golang, you can follow these steps:

Create a package-level variable of type chan bool to represent the timer channel and a variable to indicate if the timer is active.

var timerChan = make(chan bool)
var isTimerActive bool

Define a startTimer function that takes the duration of the timer as an argument.

func startTimer(duration time.Duration) {
  fmt.Println("Timer started")
  
  isTimerActive = true
  
  // Start a goroutine that waits for the specified duration and then writes to the timer channel to signal completion
  go func() {
    <-time.After(duration)
    timerChan <- true
  }()
}

Define a stopTimer function that stops the timer if it is active.

func stopTimer() {
  if isTimerActive {
    fmt.Println("Timer stopped")
    // Write to the timer channel to signal completion
    timerChan <- true
  }
}

Implement a function main to test the timer functionality.

func main() {
  // Start the timer for 3 seconds
  startTimer(3 * time.Second)
  
  // Use a select statement to wait for any of the timer completion or interrupt signal from the user
  select {
  case <-timerChan:
    fmt.Println("Timer completed")
  case <-interruptChan:
    fmt.Println("Timer interrupted")
  }
}

Run the program, and it will start the timer for 3 seconds. If the timer completes before any interruption, it will print "Timer completed". If there is an interruption, it will print "Timer interrupted".

go run main.go

Note: In this example, we assume that the interruptChan represents an interrupt signal from the user, which could be implemented using another goroutine watching for user input.