Go Channel Patterns - Wait For Result
b0r
Posted on December 12, 2021
To improve my Go Programming skills and become a better Go engineer, I have recently purchased an excellent on-demand education from Ardan Labs. Materials are created by an expert Go engineer, Bill Kennedy.
I have decide to record my process of learning how to write more idiomatic code, following Go best practices and design philosophies.
This series of posts will describe channel patterns used for orchestration/signaling in Go via goroutines.
Wait For Result Pattern
The main idea behind Wait For Result pattern is to have:
- a channel that provides a signaling semantics
- a goroutine that does some work
- a goroutine that waits for that work to be done
Example
In this example we have an employee
(a
goroutine) that has some work to do. We also have a manager
(main
goroutine) that waits on that work to be done. Once work is done, employee
notifies manager
by sending a signal (paper
) via communication channel ch
.
Feel free to try the example on Go Playground
package main
func main() {
// make channel of type string which provides signaling semantics
ch := make(chan string)
// goroutine 'a' that does some work => employee
go func() {
// simulate the idea of unknown latency (do not use in production)
time.Sleep(time.Duration(rand.Intn(500)) * time.Millisecond)
// when work is done send signal
ch <- "paper"
// we don't know the order of print statement
fmt.Println("employee: sent signal")
}()
// goroutine 'main' => manager
// goroutines 'main' and 'a' are executed in parallel
// wait for and receive signal from 'goroutine a'
// blocking operation
p := <-ch
// we don't know which print statement is going to be executed first
fmt.Println("manager: received signal :", p)
// ensure enough time to get the result (do not use in production)
time.Sleep(time.Second)
}
Result (1st execution)
go run main.go
employee: sent signal
manager: received signal : paper
Result (2st execution)
go run main.go
manager: received signal : paper
employee: sent signal
Most common misconceptions:
- Note that in the first and the second execution of the previous code, the order of
fmt.Println()
statement is not guaranteed. Goroutines are executed in parallel.
Conclusion
In this article, wait for result channel pattern was described. In addition, simple implementation was provided.
Readers are encouraged to check out excellent Ardan Labs education materials to learn more.
Resources:
Posted on December 12, 2021
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