select in Go

Waiting on whichever channel is ready first.

func race(fast, slow <-chan string) {
    for i := 0; i < 2; i++ {
        select {
        case msg := <-fast:
            fmt.Println("fast:", msg)
        case msg := <-slow:
            fmt.Println("slow:", msg)
        case <-time.After(time.Second):
            fmt.Println("timed out")
            return
        }
    }
}

How it works

1. Each case receives from a different channel.
2. The first ready case runs; ties pick randomly.
3. time.After provides a timeout arm.

Keywords and builtins used here

• case
• chan
• for
• func
• return
• select
• string

The run, in numbers

Lines

13

Characters to type

233

Tokens

74

Three-star pace

100 tpm

At the three-star pace of 100 tokens a minute, this run takes about 44 seconds.

Type this snippet

Step 1 of 3 in select, step 8 of 25 in Concurrency.

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select in other languages

• Python
• R