Difference: time.After vs time.Sleep in Go

What’s the difference between:

import "time"
<-time.After(10 * time.Second)

import "time"
time.Sleep(10 * time.Second)

The difference between <-time.After(...) and time.Sleep(...) in Go is mainly about how they interact with Go’s concurrency model and channels:

time.Sleep()

• Blocks the current goroutine for the specified duration.
• No value is produced, and you cannot select on it.
• Simple and direct: execution pauses, then resumes after the duration.

time.Sleep(10 * time.Second)
// code here runs after 10 seconds

time.After()

• Also blocks the current goroutine until the duration elapses.
• Returns a channel that receives a value after the duration.
• Can be used in a select statement, allowing you to wait for multiple events (timeouts, other channels, etc.).
• More flexible for concurrent patterns.

<-time.After(10 * time.Second)
// code here runs after 10 seconds

With select:

select {
case <-time.After(10 * time.Second):
    fmt.Println("Timeout!")
case msg := <-someChannel:
    fmt.Println("Received:", msg)
}

Summary

• Both block the goroutine if used as above.
• <-time.After(...) is more flexible and idiomatic in concurrent Go code, especially when you need to wait for either a timeout or another event.
• time.Sleep(...) is simpler for just pausing execution.