Array-port based `WaitGroup`

[emil14]

Problem

Existing sync.WaitGroup signature looks like this

def WaitGroup(count int, sig any) (sig any)

It can cover complex cases where number of tasks is unknown at compile-time, but in most cases we know that, so it's an overkill. Array-port based interface would be simpler to use:

def WaitGroup([sig] any) (sig any)

Example - Indeterministic "Hello World"

What we have

import { fmt, sync }

def Main(start any) (stop any) {
    println1 fmt.Println
	println2 fmt.Println
	wg sync.WaitGroup
    ---
    :start -> [
		'Hello' -> println1,
		', World!' -> println2
	]
    [println1, println2] -> wg:sig
    2 -> wg:count
    wg -> :stop
}

What we need

import { fmt, sync }

def Main(start any) (stop any) {
	println1 fmt.Println
	println2 fmt.Println
	wg sync.WaitGroup
	---
	:start -> [
		'Hello' -> println1 -> wg[0],
		', World!' -> println2 -> wg[1]
	]
	wg -> :stop
}

Solution

• Rename existing sync.WaitGroup to something else (figure out good naming)
• Change sync.WaitGroup interface to array-port based
• Update related examples and/or e2e tests and docs (if needed)

---

Related to #864

[emil14]

Side-note: I was thinking about HOC-based API for WaitGroup and looks like it's not possible due to the fact that Neva's DI is static (there was an issue about that, specifically not being able to have classic dynamic worker pools)