go get github.com/fdanismaz/go-executor/executor

The parallel executor is capable of running multiple independent tasks in separate go routines asynchronously. Independent here means that the execution of a task does not affect the execution of any other.

func NewParallel(concurrencyLimit int64, continueOnError bool) Executor {
    ...
}

The NewParallel function creates takes the two following parameters:

• concurrencyLimit: limits the number of tasks to be executed at the same time. If you have 100 tasks to be executed and if you want max. 3 tasks to be executed at the same time, in that case the 4th task will not be started unless one of the first three task is completed.
• continueOnError: give false to stop the executor when a task fails. Give true otherwise.

exec := executor.NewParallel(3, true)
exec.Submit(task1)
exec.Submit(task2)
exec.Submit(task3)
exec.Submit(task4)
exec.Submit(task5)
...
err := exec.execute()

The execute function returns the error of the first failed task if the continueOnError is set to false. It will be the error of the first failed task because the executor will stop when a task fails.

It returns the error of the last failed task if the continueOnError is set to true, because in that case the executor won't stop when a task fails and each time a task is failed, it will update the error variable of the executor.

It returns nil when all tasks are completed successfully.