How can I break out of a labeled for loop from outside its scope in Go?

Breaking Out of a Labeled For Loop from Outside Scope

In Go, it can be challenging to interrupt a labeled for loop from code that exists outside the loop's scope. This is common when using a go routine to perform periodic tasks and wanting to terminate the loop based on certain conditions.

Solution:

To achieve this, we can employ a signaling channel. Here's how to do it:

1. Create a Signaling Channel:

<code class="go">quit := make(chan struct{})</code>

A channel of type struct{}{} is used to send a signal that the loop should break. This channel is created outside the loop's scope.

2. Close the Channel to Signal Break:

When the condition is met to break the loop, we close the channel:

<code class="go">close(quit)</code>

By closing the channel, we signal that the go routine should terminate.

3. Modify the For Loop with a Select Statement:

Inside the labeled for loop, incorporate a select statement to listen for the signal from the channel:

<code class="go">myLoop:
  for {
    select {
    case <-quit:
      break myLoop
    default:
      // Continue looping
    }
  }

When the quit channel is closed, the select statement detects this and executes the break statement, effectively breaking out of the loop.

4. Call the Go Routine:

<code class="go">go func (){
    for {
        // Loop continues until count > 5 or quit channel is closed
        fmt.Println("I will print every second", count)
        count++ 
        if count > 5 {
          close(quit)
          wg.Done()
          return
        }
        <-t.C
    }  
  }()</code>

In this go routine, the select statement is not required because the loop is already run as a go routine and does not need to block.

By following these steps, you can break out of a labeled for loop from outside the loop's scope in Go using a signaling channel.

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