Why can't this program print anything using goroutine?

I'm recently looking into Golang by google and I met with the following problem. Then program doesn't print anything. But if I remove the "go" notations, it will print both "goroutine" and "going".

package main
import "fmt"
func f(msg string) {
	fmt.Println(msg)
	return
}
func main() {
	go f("goroutine")
	go func(msg string) {
		fmt.Println(msg)
		return
	}("going")
	return
}

You program exits before the goroutines is executed. You could wait a little bit, for example by calling time.Sleep(2 * time.Second), but such behaviour is considered bad practice, since your program could run longer than 2 seconds and would then terminate nonetheless.

A better approach is to use sync.WaitGroup:

package main
import (
	"fmt"
	"sync"
)
func f(msg string, wg *sync.WaitGroup) {
	fmt.Println(msg)
	wg.Done()
}
func main() {
	var wg sync.WaitGroup
	wg.Add(1)
	go f("goroutine", &wg)
	wg.Add(1)
	go func(msg string) {
		fmt.Println(msg)
		wg.Done()
	}("going")
	
	wg.Wait()
}

Your code needs to wait for the routines to finish before exiting. A good way to do this is to pass in a channel which is used by the routine to signal when it's done and then wait in the main code. See below.

Another advantage of this approach is that it allows/encourages you to perform proper error handling based on the return value.

package main
import (
	"fmt"
)
func f(msg string, quit chan int) {
	fmt.Println(msg)
	quit <- 0
	return
}
func main() {
	ch1 := make(chan int)
	ch2 := make(chan int)
	go f("goroutine", ch1)
	go func(msg string, quit chan int) {
		fmt.Println(msg)
		quit <- 0
		return
	}("going", ch2)
	<-ch1
	<-ch2
	return
}