doc: add function documentations.

Author: ghosind

all.go

@@ -6,14 +6,22 @@ import (
 	"sync"
 )
 
+// All executes the functions asynchronously until all functions have been finished. If some
+// function returns an error or panic, it will return the error immediately and send a cancel
+// signal to all other functions by context.
 func All(funcs ...func(context.Context) error) error {
 	return all(context.Background(), funcs...)
 }
 
+// AllWithContext executes the functions asynchronously until all functions have been finished, or
+// the context is done (canceled or timeout). If some function returns an error or panic, it will
+// return the error immediately and send a cancel signal to all other functions by context.
 func AllWithContext(ctx context.Context, funcs ...func(context.Context) error) error {
 	return all(ctx, funcs...)
 }
 
+// all executes the functions asynchronously until all functions have been finished, or the context
+// is done (canceled or timeout).
 func all(parent context.Context, funcs ...func(context.Context) error) error {
 	if len(funcs) == 0 {
 		return nil
@@ -71,15 +79,30 @@ func all(parent context.Context, funcs ...func(context.Context) error) error {
 	}
 }
 
+// AllCompleted executes the functions asynchronously until all functions have been finished. It
+// will return an error slice that is ordered by the functions order, and a boolean value to
+// indicate whether any functions return an error or panic.
 func AllCompleted(funcs ...func(context.Context) error) ([]error, bool) {
 	return allCompleted(context.Background(), funcs...)
 }
 
-func AllCompletedWithContext(ctx context.Context, funcs ...func(context.Context) error) ([]error, bool) {
+// AllCompletedWithContext executes the functions asynchronously until all functions have been
+// finished, or the context is done (canceled or timeout). It will return an error slice that is
+// ordered by the functions order, and a boolean value to indicate whether any functions return an
+// error or panic.
+func AllCompletedWithContext(
+	ctx context.Context,
+	funcs ...func(context.Context) error,
+) ([]error, bool) {
 	return allCompleted(ctx, funcs...)
 }
 
-func allCompleted(parent context.Context, funcs ...func(context.Context) error) (errs []error, hasError bool) {
+// allCompleted executes the functions asynchronously until all functions have been finished, or
+// the context is done (canceled or timeout).
+func allCompleted(
+	parent context.Context,
+	funcs ...func(context.Context) error,
+) (errs []error, hasError bool) {
 	hasError = false
 	errs = make([]error, len(funcs))
 	if len(funcs) == 0 {

race.go

@@ -5,14 +5,21 @@ import (
 	"sync/atomic"
 )
 
+// Race executes the functions asynchronously, it will return the result of the first of the
+// finished function (including panic), and it will not send a cancel signal to other functions.
 func Race(funcs ...func(context.Context) error) error {
 	return race(context.Background(), funcs...)
 }
 
+// RaceWithContext executes the functions asynchronously, it will return the result of the first of
+// the finished function (including panic), and it will not send a cancel signal to other
+// functions.
 func RaceWithContext(ctx context.Context, funcs ...func(context.Context) error) error {
 	return race(ctx, funcs...)
 }
 
+// race executes the functions asynchronously, it will return the result of the first of the
+// finished function (including panic).
 func race(ctx context.Context, funcs ...func(context.Context) error) error {
 	if len(funcs) == 0 {
 		return nil