Task cancellation

As explained in Go in Action, Second Edition

A cancellation signal is an indication that ongoing work should stop because it is no longer needed.

Task cancellation signals that ongoing work is no longer needed and should stop. In a Go service, a context carries that signal through the request call chain, allowing downstream goroutines, database operations, and HTTP calls to wind down instead of continuing after a client disconnects or deadline. section 1.4.3 section 1.4.2

Use cancellation to keep concurrent work bounded and responsive:

• Create a context with a timeout when the operation has a known time budget. section 9.3
• Pass contexts as values through function calls rather than embedding them in structs. section 9.3
• Derive contexts for groups of concurrent operations so one error can cancel the remaining work. section 9.3
• Call the cancel function when the operation ends, and use context for both cancellation and deadlines. section 9.3 section 9.6.1

Canceling concurrent feed fetches

A feed aggregator creates a 60-second context, passes it to each fetch, and derives an errgroup context. If one feed fetch fails, the derived context cancels the other requests; if the deadline expires, all downstream operations can return early. section 9.3

Figure 1.4 The life cycle of a single HTTP request

Trace cancellation from an HTTP client disconnect or deadline through the request goroutine and its downstream operations. section 1.4.3

How Go in Action, Second Edition covers it

How deep it goes

Explains propagation, timeouts, derived contexts, deferred cancellation, and errgroup coordination without detailing context internals.

Examples

Uses an HTTP request lifecycle and concurrent RSS feed fetching with a 60-second timeout and error-triggered cancellation.

What it assumes

Assumes goroutines and channels, while introducing context propagation, cancellation, deadlines, and coordinated concurrent shutdown.

What you can do after

Apply it via context.Context and errgroup to stop timed-out or failed concurrent operations and release downstream work.

How it connects

Connects cancellation to contexts, deadlines, goroutines, channels, HTTP requests, database operations, and error groups.

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Also explained in

• 

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  Kotlin in Action, 2E
• 

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  Go by ExampleA cancellation signal is an indication that an ongoing operation should stop because it is no longer needed or cannot continue.
• 

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  Python Concurrency with asyncioTask cancellation is the cooperative termination of an asynchronous task by requesting that it stop at a cancellation point.
• 

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  100 Go Mistakes and How to Avoid ThemContext cancellation is the signaling of a context's invalidation so operations observing it can stop or abort their work.

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Related concepts

• contextused by · In Go, context.Context is an interface carrying cancellation signals, deadlines, and request-scoped values across function and service boundaries.
• CancelledErrorproduces · CancelledError is the asyncio exception raised in a task when cancellation is delivered while the task is being awaited or resumed.
• coroutine hierarchyuses · A coroutine hierarchy is a parent-child organization of coroutines through which execution lifetimes and failures can be related.
• CancellationExceptionuses · CancellationException is an exception used by Kotlin coroutines to signal that a coroutine has been cancelled.
• context packageproduced by · The context package is Go’s standard-library package for propagating cancellation, deadlines, timeouts, and request-scoped values across call boundaries.

This explainer was generated by Manning's knowledge graph from the text of Go in Action, Second Edition. The section links point to the parts of the book it draws on.