select with default in Go

A default case makes select non-blocking, which is how you poll.

func poll(jobs chan int) string {
    select {
    case job := <-jobs:
        return fmt.Sprintf("got %d", job)
    default:
        return "nothing waiting"
    }
}

func trySend(jobs chan int, job int) bool {
    select {
    case jobs <- job:
        return true
    default:
        return false // queue full, drop it
    }
}

How it works

1. Without default, select waits for a ready case.
2. With default, it takes that branch immediately when nothing is ready.
3. Ready cases are chosen at random, so no case starves.

Keywords and builtins used here

• bool
• case
• chan
• default
• func
• int
• return
• select
• string

The run, in numbers

Lines

17

Characters to type

267

Tokens

60

Three-star pace

100 tpm

At the three-star pace of 100 tokens a minute, this run takes about 36 seconds.

Type this snippet

Step 2 of 3 in select, step 9 of 25 in Concurrency.

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