I'm kind of lost here, I was trying to get a goroutine to add to an array and another goroutine to read from it, which I suspect is somewhat close to what I have below but I need to play around with the wait().
However, I am getting the error prog.go:19:14: too many variables in range, line 19 is for _, v := range c { I can't find an answer for that online, what am I doing or not doing here?
package main
import (
"fmt"
//"time"
"sync"
)
func hello(wg *sync.WaitGroup, s []int, c chan int) {
for _, v := range s {
c <- v
}
fmt.Println("Finished adding to channel")
wg.Done()
}
func hello2(wg *sync.WaitGroup, c chan int) {
fmt.Println("Channel",c)
for _, v := range c {
fmt.Println("Received",v)
}
fmt.Println("Finished taking from channel")
wg.Done()
}
func main() {
s := []int{1, 2, 3, 4, 5}
var c = make(chan int, 5)
var wg sync.WaitGroup
wg.Add(1)
go hello(&wg, s, c)
wg.Wait()
wg.Add(1)
go hello2(&wg, c)
wg.Wait()
//time.Sleep(1 * time.Second)
fmt.Println("main function")
}
When you range over a channel, iterations only produce a single value, the values that were sent on the channel. There is no index or key value like in case of slices or maps.
So you must use:
for v := range c {
fmt.Println("Received", v)
}
This is detailed in Spec: For statements:
If the range expression is a channel, at most one iteration variable is permitted, otherwise there may be up to two.
And:
For channels, the iteration values produced are the successive values sent on the channel until the channel is closed. If the channel is
nil, the range expression blocks forever.
And also:
Function calls on the left are evaluated once per iteration. For each iteration, iteration values are produced as follows if the respective iteration variables are present:
Range expression 1st value 2nd value array or slice a [n]E, *[n]E, or []E index i int a[i] E string s string type index i int see below rune map m map[K]V key k K m[k] V channel c chan E, <-chan E element e E