Multiple goroutines listening on one channel

Question

I have multiple goroutines trying to receive on the same channel simultaneously. It seems like the last goroutine that starts receiving on the channel gets the value. Is thi

Answer 1

It is complicated.

Also, see what happens with GOMAXPROCS = NumCPU+1. For example,

package main

import (
    "fmt"
    "runtime"
)

func main() {
    runtime.GOMAXPROCS(runtime.NumCPU() + 1)
    fmt.Print(runtime.GOMAXPROCS(0))
    c := make(chan string)
    for i := 0; i < 5; i++ {
        go func(i int) {
            msg := <-c
            c <- fmt.Sprintf("%s, hi from %d", msg, i)
        }(i)
    }
    c <- ", original"
    fmt.Println(<-c)
}

Output:

5, original, hi from 4

And, see what happens with buffered channels. For example,

package main

import "fmt"

func main() {
    c := make(chan string, 5+1)
    for i := 0; i < 5; i++ {
        go func(i int) {
            msg := <-c
            c <- fmt.Sprintf("%s, hi from %d", msg, i)
        }(i)
    }
    c <- "original"
    fmt.Println(<-c)
}

Output:

original

You should be able to explain these cases too.