Go select and Timeouts

select waits on several channel operations at once. With time.After it gives you timeouts.

ExampleGo

package main

import (
  "fmt"
  "time"
)

func main() {
  fast := make(chan string)
  slow := make(chan string)

  go func() {
    time.Sleep(10 * time.Millisecond)
    fast <- "fast result"
  }()
  go func() {
    time.Sleep(500 * time.Millisecond)
    slow <- "slow result"
  }()

  for i := 0; i < 2; i++ {
    select {
    case m := <-fast:
      fmt.Println(m)
    case m := <-slow:
      fmt.Println(m)
    case <-time.After(100 * time.Millisecond):
      fmt.Println("timeout")
    }
  }
}

Output

fast result
timeout

Quick check

What does select do?

Waits for one of several channel operationsChooses a random functionSelects rows from a database

Finish the quick check (and any code exercise) to complete this lesson, or mark it done yourself.

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