Standard library · Time and concurrency

ctx

A context for cancellation and deadlines, passed from the main piece of work down to the smaller ones.

import ctx

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Types
Functions

A context tells long-running work when to stop: either someone called Cancel, or its deadline passed. Contexts form a tree: you start from Background and make a child each time with WithCancel, WithTimeout or WithDeadline.

Cancelling a context ends all its children, but not its parent. The work should check IsDone from time to time, or wait on it with Wait. Free each context with Free when you are done with it, children before parents.

Types

`Context`

struct Context

A context.

Name	Type	Description
`state`	`i64*`	The internal state: cancelled, the deadline and whether there is one.
`parent`	`Context*`	The parent context, or null for the root.
`mu`	`sync.Mutex`	The lock every context in one tree shares.
`cv`	`sync.CondVar`	The condition variable that cancellation wakes.
`is_root`	`bool = false`	Whether this context is the root.

ctx-Context.salam

import ctx

func main:
    root := ctx.Background()
    cancellable := ctx.WithCancel(root)
    timed := ctx.WithTimeout(cancellable, 30)
    println ctx.IsDone(timed), "[" + ctx.Err(timed) + "]", ctx.Deadline(timed) > 0, ctx.Deadline(root)
    println ctx.Wait(timed, 10)
    println ctx.Wait(timed, 1000), ctx.Err(timed)
    ctx.Cancel(cancellable)
    println ctx.IsDone(cancellable), ctx.Err(cancellable), ctx.IsDone(root)
    past := ctx.WithDeadline(root, 1)
    println ctx.IsDone(past), ctx.Err(past)
    ctx.Free(past)
    ctx.Free(timed)
    ctx.Free(cancellable)
    ctx.Free(root)
end

Outputfalse [] true 0 false true deadline exceeded true cancelled false true deadline exceeded