Goroutines

Goroutines

Creating Goroutines

use go keyword in front of function call

when using anonymous functions, pass data as local variables (arguments)

package main

import (
    "fmt"
    "sync"
)

var wg = sync.WaitGroup{}

func main() {
    var msg string = "Hello"
    wg.Add(1)

    go func(msh string) {
        fmt.Println(msg)
        wg.Done()   
    }(msg)

    wg.Wait()
}

Synchronization

WaitGroups

use sync.WaitGroup to wait for groups of goroutines to complete
Add : to inform the wait group that here are more goroutines for it to wait on
Wait: block the goroutine that is called until with wait group is compleded
Done: let wait group that one of the goroutine is completed

Mutexes

Use synce.Mutexe and synce.RWMutex to protect data access
to ensure only one goroutine is manipulating the data at one time

package main

import (
    "fmt"
    "sync"
)

var wg sync.WaitGroup = sync.WaitGroup{}
var counter int = 0
var m sync.RWMutex = sync.RWMutex{}

func main() {
    for i := 0; i < 10; i++ {
        wg.Add(2)
        m.RLock()
        go sayHello()
        m.Lock()
        go increment()
    }
    wg.Wait()
}

func sayHello() {
    fmt.Printf("Hello #%v\n", counter)
    m.RUnlock()
    wg.Done()
}

func increment() {
    counter++
    m.Unlock()
    wg.Done()
}

Parallelism

By default , Go will use CPU threads equal to available cores
Change with runtime.GOMAXPROCS
More threads can increase performance, but to many can slow it down
- test when getting close to production

Best Practices

Don't create goroutines in libraries
let consumer control concurrency
When creating a goroutine, know how it will end
avoid subtle memory leaks
check for race conditions at compile time
```
go run -race main.go
```