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54 lines
1.4 KiB
Go
54 lines
1.4 KiB
Go
// _Timeouts_ are important for programs that connect to
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// external resources or that otherwise need to bound
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// execution time. Implementing timeouts in Go is easy and
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// elegant thanks to channels and `select`.
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package main
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import (
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"fmt"
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"time"
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)
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func main() {
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// For our example, suppose we're executing an external
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// call that returns its result on a channel `c1`
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// after 2s. Note that the channel is buffered, so the
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// send in the goroutine is nonblocking. This is a
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// common pattern to prevent goroutine leaks in case the
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// channel is never read.
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c1 := make(chan string, 1)
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go func() {
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time.Sleep(2 * time.Second)
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c1 <- "result 1"
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}()
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// Here's the `select` implementing a timeout.
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// `res := <-c1` awaits the result and `<-Time.After`
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// awaits a value to be sent after the timeout of
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// 1s. Since `select` proceeds with the first
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// receive that's ready, we'll take the timeout case
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// if the operation takes more than the allowed 1s.
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select {
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case res := <-c1:
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fmt.Println(res)
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case <-time.After(1 * time.Second):
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fmt.Println("timeout 1")
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}
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// If we allow a longer timeout of 3s, then the receive
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// from `c2` will succeed and we'll print the result.
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c2 := make(chan string, 1)
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go func() {
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time.Sleep(2 * time.Second)
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c2 <- "result 2"
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}()
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select {
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case res := <-c2:
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fmt.Println(res)
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case <-time.After(3 * time.Second):
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fmt.Println("timeout 2")
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}
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}
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