package main

import (
    "time"
    "context"
    "fmt"
)

func main() {
    d := time.Now().Add(50*time.Millisecond)
    ctx, cancel := context.WithDeadline(context.Background(), d)
    defer cancel()

    select {
    case <-time.After(1*time.Second):
        fmt.Println("overslept")
    case <-ctx.Done():
        fmt.Println(ctx.Err())
    }
}

context deadline exceeded