在select中的同一通道上读写

Question

Is it OK to exchange data between two routines using one channel this way?

c := make(chan int)

go func() {
    var i int
    select {
    case c<- 1:
        i = <-c
    case i = <-c:
        c<- 1
    }
    fmt.Println(" A - Written 1 red ", i)
}()

var i int
select {
case c<- 2:
    i = <-c
case i = <-c:
    c<- 2
}
fmt.Println(" B - Written 2 red ", i)

Answer 1

It works, but is generally a bad idea(tm)

your future software maintainers will hate you for it

Note, if those loops are not exactly the same, then the app will crash with when the main goroutine blocks due to noone else writing or reading

package main

import (
    "fmt"
)

func main() {
    c := make(chan int)

    go func() {
        for x := 0; x < 5; x++ {
            var i int
            select {
            case c <- 1:
                i = <-c
            case i = <-c:
                c <- 1
            }
            fmt.Println(" A - Written 1 red ", i)
        }
    }()
    for x := 0; x < 5; x++ {
        var i int
        select {
        case c <- 2:
            i = <-c
        case i = <-c:
            c <- 2
        }
        fmt.Println(" B - Written 2 red ", i)
    }
}

Output:

 B - Written 2 red  1
 A - Written 1 red  2
 B - Written 2 red  1
 A - Written 1 red  2
 B - Written 2 red  1
 A - Written 1 red  2
 B - Written 2 red  1
 A - Written 1 red  2
 B - Written 2 red  1

Program exited.