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Gopher Floc Control


Floc: Orchestrate goroutines with ease.

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The goal of the project is to make the process of running goroutines in parallel and synchronizing them easy.


v3 released! The new version keeps the same design as v2 but it distributed now as a Go module and therefore it has breaking changes.

Migration from v2 to v3

  1. Install the package with go get
  2. Replace all old paths to
  3. All types from errors sub-package moved to the base package go-floc. So please, remove all imports of "" if any and fix type names, e.g. errors.ErrTimeout -> floc.ErrTimeout

Installation and requirements

The package requires Go v1.12 or later.

To install the package use go get

Documentation and examples

Please refer Godoc reference of the package for more details.

Some examples are available at the Godoc reference. Additional examples can be found in go-floc-showcase.


  • Easy to use functional interface.
  • Simple parallelism and synchronization of jobs.
  • As little overhead as possible, in comparison to direct use of goroutines and sync primitives.
  • Provide better control over execution with one entry point and one exit point.


Floc introduces some terms which are widely used through the package.


Flow is the overall process which can be controlled through floc.Flow. Flow can be canceled or completed with any arbitrary data at any point of execution. Flow has only one enter point and only one exit point.

// Design the job
flow := run.Sequence(do, something, here, ...)

// The enter point: Run the job
result, data, err := floc.Run(flow)

// The exit point: Check the result of the job.
if err != nil {
	// Handle the error
} else if result.IsCompleted() {
	// Handle the success
} else {
	// Handle other cases


Job in Floc is a smallest piece of flow. The prototype of job function is floc.Job. Each job can read/write data with floc.Context and control the flow with floc.Control.

Cancel(), Complete(), Fail() methods of floc.Flow has permanent effect. Once finished flow cannot be canceled or completed anymore. Calling Fail and returning error from job is almost equal.

func ValidateContentLength(ctx floc.Context, ctrl floc.Control) error {
  request := ctx.Value("request").(http.Request)

  // Cancel the flow with error if request body size is too big
  if request.ContentLength > MaxContentLength {
    return errors.New("content is too big")
  return nil


Lets have some fun and write a simple example which calculates some statistics on text given.

const Text = `Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed
  do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim
  veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
  consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum
  dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident,
  sunt in culpa qui officia deserunt mollit anim id est laborum.`

type myKey int
const keyStatistics myKey = 1

var sanitizeWordRe = regexp.MustCompile(`\W`)

type Statistics struct {
  Words      []string
  Characters int
  Occurrence map[string]int

// Split to words and sanitize them
SplitToWords := func(ctx floc.Context, ctrl floc.Control) error {
  statistics := ctx.Value(keyStatistics).(*Statistics)

  statistics.Words = strings.Split(Text, " ")
  for i, word := range statistics.Words {
    statistics.Words[i] = sanitizeWordRe.ReplaceAllString(word, "")
  return nil

// Count and sum the number of characters in the each word
CountCharacters := func(ctx floc.Context, ctrl floc.Control) error {
  statistics := ctx.Value(keyStatistics).(*Statistics)

  for _, word := range statistics.Words {
    statistics.Characters += len(word)
  return nil

// Count the number of unique words
CountUniqueWords := func(ctx floc.Context, ctrl floc.Control) error {
  statistics := ctx.Value(keyStatistics).(*Statistics)

  statistics.Occurrence = make(map[string]int)
  for _, word := range statistics.Words {
    statistics.Occurrence[word] = statistics.Occurrence[word] + 1
  return nil

// Print result
PrintResult := func(ctx floc.Context, ctrl floc.Control) error {
  statistics := ctx.Value(keyStatistics).(*Statistics)

  fmt.Printf("Words Total       : %d\n", len(statistics.Words))
  fmt.Printf("Unique Word Count : %d\n", len(statistics.Occurrence))
  fmt.Printf("Character Count   : %d\n", statistics.Characters)
  return nil

// Design the flow and run it
flow := run.Sequence(

ctx := floc.NewContext()
ctx.AddValue(keyStatistics, new(Statistics))

ctrl := floc.NewControl(ctx)

_, _, err := floc.RunWith(ctx, ctrl, flow)
if err != nil {

// Output:
// Words Total       : 64
// Unique Word Count : 60
// Character Count   : 370


Please found information about contributing in and the list of braves who spent their priceless time and effort to make the project better in