github.com/jrperritt/terraform@v0.1.1-0.20170525065507-96f391dafc38/helper/slowmessage/slowmessage.go (about)

     1  package slowmessage
     2  
     3  import (
     4  	"time"
     5  )
     6  
     7  // SlowFunc is the function that could be slow. Usually, you'll have to
     8  // wrap an existing function in a lambda to make it match this type signature.
     9  type SlowFunc func() error
    10  
    11  // CallbackFunc is the function that is triggered when the threshold is reached.
    12  type CallbackFunc func()
    13  
    14  // Do calls sf. If threshold time has passed, cb is called. Note that this
    15  // call will be made concurrently to sf still running.
    16  func Do(threshold time.Duration, sf SlowFunc, cb CallbackFunc) error {
    17  	// Call the slow function
    18  	errCh := make(chan error, 1)
    19  	go func() {
    20  		errCh <- sf()
    21  	}()
    22  
    23  	// Wait for it to complete or the threshold to pass
    24  	select {
    25  	case err := <-errCh:
    26  		return err
    27  	case <-time.After(threshold):
    28  		// Threshold reached, call the callback
    29  		cb()
    30  	}
    31  
    32  	// Wait an indefinite amount of time for it to finally complete
    33  	return <-errCh
    34  }