WithDeadline

Learn context bound to a specific time with WithDeadline.

WithDeadline

While WithTimeout takes a relative duration, WithDeadline takes an absolute time.Time. In fact WithTimeout(ctx, d) is shorthand for WithDeadline(ctx, time.Now().Add(d)).

son := time.Date(2026, 12, 31, 23, 59, 0, 0, time.UTC)
ctx, cancel := context.WithDeadline(context.Background(), son)
defer cancel()

if d, ok := ctx.Deadline(); ok {
    fmt.Println("kalan:", time.Until(d))
}

Propagating the deadline

The remaining time can be read with ctx.Deadline() and adapted for subsystems. For example, gRPC and many database drivers pass the ctx deadline to the server, so when the client gives up the server stops working too. Not starting an expensive job at all when the remaining time is very short is also a good optimization.

Exercise Past deadline

Pass time.Now().Add(-time.Second) to context.WithDeadline. Write defer cancel() and print ctx.Err().

Show example solution

package main

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

func main() {
    ctx, cancel := context.WithDeadline(context.Background(), time.Now().Add(-time.Second))
    defer cancel()
    fmt.Println(ctx.Err())
}

Test yourself

What happens if <code>WithDeadline</code> is called with a date in the past?
- It is never cancelled
- It is cancelled a day later
- The context comes back already cancelled
- It panics
Show answer

The context comes back already cancelled — If the deadline has passed, the context is already in DeadlineExceeded; its Done channel is closed.

Read the deadline

if d, ok := ctx.____(); ok {
    fmt.Println(time.Until(d))
}

Show answer

if d, ok := ctx.Deadline(); ok {
    fmt.Println(time.Until(d))
}

Function and argument

WithTimeout

Relative duration
WithDeadline

Absolute time
ctx.Deadline()

Deadline and ok
time.Until(d)

Remaining time

Next lesson: Summary - Context

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