Best approach to getting results out of goroutines - go

Question

I have two functions that I cannot change (see first() and second() below). They are returning some data and errors (the output data is different, but in the examples below I use (string, error) for simplicity)
I would like to run them in separate goroutines - my approach:
package main
import (
"fmt"
"os"
)
func first(name string) (string, error) {
if name == "" {
return "", fmt.Errorf("empty name is not allowed")
}
fmt.Println("processing first")
return fmt.Sprintf("First hello %s", name), nil
}
func second(name string) (string, error) {
if name == "" {
return "", fmt.Errorf("empty name is not allowed")
}
fmt.Println("processing second")
return fmt.Sprintf("Second hello %s", name), nil
}
func main() {
firstCh := make(chan string)
secondCh := make(chan string)
go func() {
defer close(firstCh)
res, err := first("one")
if err != nil {
fmt.Printf("Failed to run first: %v\n", err)
}
firstCh <- res
}()
go func() {
defer close(secondCh)
res, err := second("two")
if err != nil {
fmt.Printf("Failed to run second: %v\n", err)
}
secondCh <- res
}()
resultsOne := <-firstCh
resultsTwo := <-secondCh
// It's important for my app to do error checking and stop if errors exist.
if resultsOne == "" || resultsTwo == "" {
fmt.Println("There was an ERROR")
os.Exit(1)
}
fmt.Println("ONE:", resultsOne)
fmt.Println("TWO:", resultsTwo)
}
I believe one caveat is that resultsOne := <- firstCh blocks until first goroutine finishes, but I don't care too much about this.
Can you please confirm that my approach is good? What other approaches would be better in my situation?

Answer 1

The example looks mostly good. A couple improvements are:
declaring your channels as buffered
firstCh := make(chan string, 1)
secondCh := make(chan string, 1)
With unbuffered channels, send operations block (until someone receives). If your goroutine #2 is much faster than the first, it will have to wait until the first finishes as well, since you receive in sequence:
resultsOne := <-firstCh // waiting on this one first
resultsTwo := <-secondCh // sender blocked because the main thread hasn't reached this point
use "golang.org/x/sync/errgroup".Group. The program will feel "less native" but it dispenses you from managing channels by hand — which trades, in a non-contrived setting, for sync'ing writes on the results:
func main() {
var (
resultsOne string
resultsTwo string
)
g := errgroup.Group{}
g.Go(func() error {
res, err := first("one")
if err != nil {
return err
}
resultsOne = res
return nil
})
g.Go(func() error {
res, err := second("two")
if err != nil {
return err
}
resultsTwo = res
return nil
})
err := g.Wait()
// ... handle err