Wait result of multiple goroutines

Question

I am searching a way to execute asynchronously two functions in go which returns different results and errors, wait for them to finish and print both results. Also if one of

Answer 1

I have created a smaller, self-contained example of how you can have two go routines run asynchronously and wait for both to finish or quit the program if an error occurs (see below for an explanation):

package main

import (
    "errors"
    "fmt"
    "math/rand"
    "time"
)

func main() {
    rand.Seed(time.Now().UnixNano())

    // buffer the channel so the async go routines can exit right after sending
    // their error
    status := make(chan error, 2)

    go func(c chan<- error) {
        if rand.Intn(2) == 0 {
            c <- errors.New("func 1 error")
        } else {
            fmt.Println("func 1 done")
            c <- nil
        }
    }(status)

    go func(c chan<- error) {
        if rand.Intn(2) == 0 {
            c <- errors.New("func 2 error")
        } else {
            fmt.Println("func 2 done")
            c <- nil
        }
    }(status)

    for i := 0; i < 2; i++ {
        if err := <-status; err != nil {
            fmt.Println("error encountered:", err)
            break
        }
    }
}

What I do is create a channel that is used for synchronization of the two go routines. Writing to and reading from it blocks. The channel is used to pass the error value around, or nil if the function succeeds.

At the end I read one value per async go routine from the channel. This blocks until a value is received. If an error occurs, I exit the loop, thus quitting the program.

The functions either succeed or fail randomly.

I hope this gets you going on how to coordinate go routines, if not, let me know in the comments.

Note that if you run this in the Go Playground, the rand.Seed will do nothing, the playground always has the same "random" numbers, so the behavior will not change.