How to select in Go?

Question

In Unix select is used to wait for more than one input source. Select waits until one input source becomes ready.

How to do this in Go?

I found a Select in Go but this seams to be a thin wrapper around the Unix function, because it works on file descriptors.

How to wait for more than one connection, in particular UnixConn connections used for Unix Domain Sockets?

@CeriseLimón I need the input from the two connections in one function. Like an adder: read `a` from connection 1, `b` from connection 2 and return `a+b`. The function should not care, which value arrives first, but should wait until both values have been read. — ceving, Mar 26 '19 at 16:52
Then you not even need a select, just read from both, e.g. from two goroutines and combine via one channel and to receives. — Volker, Mar 26 '19 at 20:34

score 1 · Accepted Answer · answered Mar 26 '19 at 17:53

package main

import (
    "fmt"
)

type Message struct {
    Payload int
}

func main() {
    var inA *Message
    var inB *Message

    rxA := make(chan *Message)
    rxB := make(chan *Message)

    go func(txA chan *Message){
      txA <- &Message{Payload: 1} 
    }(rxA)

    go func(txB chan *Message){
      txB <- &Message{Payload: 2} 
    }(rxB)

    for {
        select {
            case inA = <- rxA:
            case inB = <- rxB:
        }
        if inA != nil && inB != nil {
            fmt.Println(inA.Payload + inB.Payload)
            break
        }
    }
}

I see, `select` is syntax in Go. I was looking for a function. — ceving, Mar 27 '19 at 07:46

How to select in Go?

1 Answers1