GO language: fatal error: all goroutines are asleep - deadlock

Question

Code below works fine with hard coded JSON data however doesn\'t work when I read JSON data from a file. I\'m getting fatal error: all goroutines are asleep - deadlock

Answer 1

Thanks for the very nice and detailed explanation Grzegorz Żur. One thing that I want to point it out that typically the func that needs to be threaded wont be in main(), so we would have something like this:

package main

import (
    "bufio"
    "fmt"
    "io"
    "io/ioutil"
    "math/rand"
    "os"
    "reflect"
    "regexp"
    "strings"
    "sync"
    "time"
)

var wg sync.WaitGroup    // VERY IMP to declare this globally, other wise one   //would hit "fatal error: all goroutines are asleep - deadlock!"

func doSomething(arg1 arg1Type) {
     // cured cancer
}

func main() {
    r := rand.New(rand.NewSource(time.Now().UnixNano()))
    randTime := r.Intn(10)
    wg.Add(1)    
    go doSomething(randTime)
    wg.Wait()
    fmt.Println("Waiting for all threads to finish")
}

The thing that I want to point it out is that global declaration of wg is very crucial for all threads to finish before main()