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package main

import (
    "runtime"
    "sync"
)

func main() {
    println("GOMAXPROCS", runtime.GOMAXPROCS(0))
    n := 5
    var wg sync.WaitGroup
    wg.Add(n)
    ch := make(chan int, n)
    for i := 0; i < n; i++ {
        println("Processing ", i)
        go process(i, ch)
        go consume(ch, &wg)
    }
    wg.Wait()
    println("Finished the process")
}

func consume(ch chan int, wg *sync.WaitGroup) {
    defer wg.Done()
    println("Result ", <-ch)
}

func process(i int, ch chan int) {
    ch <- (i * 5)
}

Playground: https://play.golang.org/p/pfZTmmVw0lU

package main

import (
    "runtime"
    "sync"
)

func main() {
    println("GOMAXPROCS", runtime.GOMAXPROCS(0))
    var wg sync.WaitGroup
    n := 5
    ch := make(chan int, n)
    for i := 0; i < n; i++ {
        println("Processing ", i)
        go process(i, ch)
        wg.Add(1)
        go consume(ch, &wg)
    }
    wg.Wait()
    println("Finished the process")
}

func consume(ch chan int, wg *sync.WaitGroup) {
    defer wg.Done()
    println("Result ", <-ch)
}

func process(i int, ch chan int) {
    ch <- (i * 5)
}

Playground: https://play.golang.org/p/3czBixAjxdT

Run the Go race detector to check for data races. It finds none.

Run the Go data race detector to check for data races. It finds none.

Every time you execute a go statement it is passed to the scheduler. What if scheduling is delayed? wg.Add(1) is not executed and wg.Wait() is true. For example, run your code in the Go Playground.

package main

import (
    "sync"
)

func main() {
    n := 5
    var wg sync.WaitGroup
    wg.Add(n)
    ch := make(chan int, n)
    for i := 0; i < n; i++ {
        println("Processing ", i)
        go process(i, ch)
        go consume(ch, &wg)
    }
    wg.Wait()
    println("Finished the process")
}

func consume(ch chan int, wg *sync.WaitGroup) {
    defer wg.Done()
    println("Result ", <-ch)
}

func process(i int, ch chan int) {
    ch <- (i * 5)
}

Playground: https://play.golang.org/p/rBp62M4_PwU

Processing  0
Processing  1
Processing  2
Processing  3
Processing  4
Result  0
Result  5
Result  10
Result  15
Result  20
Finished the process

$ go run -race waiting.go
Processing  0
Processing  1
Result  0
Processing  2
Result  5
Processing  3
Result  10
Processing  4
Result  15
Result  20
Finished the process
$ 

Every time you execute a go statement it is passed to the scheduler. What if scheduling is delayed? wg.Add(1) is not executed and wg.Wait() is true. For example, run your code in the Go Playground where GOMAXPROCS is 1.

package main

import (
    "runtime"
    "sync"
)

func main() {
    println("GOMAXPROCS", runtime.GOMAXPROCS(0))
    n := 5
    var wg sync.WaitGroup
    wg.Add(n)
    ch := make(chan int, n)
    for i := 0; i < n; i++ {
        println("Processing ", i)
        go process(i, ch)
        go consume(ch, &wg)
    }
    wg.Wait()
    println("Finished the process")
}

func consume(ch chan int, wg *sync.WaitGroup) {
    defer wg.Done()
    println("Result ", <-ch)
}

func process(i int, ch chan int) {
    ch <- (i * 5)
}

Playground: https://play.golang.org/p/pfZTmmVw0lU

GOMAXPROCS 1
Processing  0
Processing  1
Processing  2
Processing  3
Processing  4
Result  0
Result  5
Result  10
Result  15
Result  20
Finished the process

$ go run -race waiting.go
GOMAXPROCS 4
Processing  0
Processing  1
Result  0
Processing  2
Result  5
Processing  3
Result  10
Processing  4
Result  15
Result  20
Finished the process
$