How to make a channel that receive multiple return values from a goroutine

I have a function in Go that returns two values. I want to run this as a goroutine, but I can't figure out the syntax for creating a channel that receives two values. Could someone point me in the right direction?

Solution 1:

Define a custom type with fields for both values, then create a chan of that type.

EDIT: I've also added an example (right at the bottom) that uses multiple channels rather than a custom type. I'm not sure which is more idiomatic.

For example:

type Result struct {
    Field1 string
    Field2 int
}

then

ch := make(chan Result)

Example of using a channel of a custom type (Playground):

package main

import (
    "fmt"
    "strings"
)

type Result struct {
    allCaps string
    length  int
}

func capsAndLen(words []string, c chan Result) {
    defer close(c)
    for _, word := range words {
        res := new(Result)
        res.allCaps = strings.ToUpper(word)
        res.length = len(word)
        c <- *res       
    }
}

func main() {
    words := []string{"lorem", "ipsum", "dolor", "sit", "amet"}
    c := make(chan Result)
    go capsAndLen(words, c)
    for res := range c {
        fmt.Println(res.allCaps, ",", res.length)
    }
}

Produces:

LOREM , 5
IPSUM , 5
DOLOR , 5
SIT , 3
AMET , 4

EDIT: Example using multiple channels instead of a custom type to produce the same output (Playground):

package main

import (
    "fmt"
    "strings"
)

func capsAndLen(words []string, cs chan string, ci chan int) {
    defer close(cs)
    defer close(ci)
    for _, word := range words {
        cs <- strings.ToUpper(word)
        ci <- len(word)
    }
}

func main() {
    words := []string{"lorem", "ipsum", "dolor", "sit", "amet"}
    cs := make(chan string)
    ci := make(chan int)
    go capsAndLen(words, cs, ci)
    for allCaps := range cs {
        length := <-ci
        fmt.Println(allCaps, ",", length)
    }
}

Solution 2:

Another option would be to use an anon function like so:

package main

import "fmt"

func f(c chan func() (int, string)) {
    c <- (func() (int, string) { return 0, "s" })
}

func main() {
    c := make(chan func() (int, string))
    go f(c)
    y, z := (<-c)()
    fmt.Println(y)
    fmt.Println(z)
}

Credit to https://gist.github.com/slav/ca2ee333c29b8f76b557c9b10b371b52