Namespace: go.std.context




Provides a low-level interface to the context package.

Package context defines the Context type, which carries deadlines,
cancellation signals, and other request-scoped values across API boundaries
and between processes.

Incoming requests to a server should create a Context, and outgoing
calls to servers should accept a Context. The chain of function
calls between them must propagate the Context, optionally replacing
it with a derived Context created using WithCancel, WithDeadline,
WithTimeout, or WithValue. When a Context is canceled, all
Contexts derived from it are also canceled.

The WithCancel, WithDeadline, and WithTimeout functions take a
Context (the parent) and return a derived Context (the child) and a
CancelFunc. Calling the CancelFunc cancels the child and its
children, removes the parent's reference to the child, and stops
any associated timers. Failing to call the CancelFunc leaks the
child and its children until the parent is canceled or the timer
fires. The go vet tool checks that CancelFuncs are used on all
control-flow paths.

Programs that use Contexts should follow these rules to keep interfaces
consistent across packages and enable static analysis tools to check context

Do not store Contexts inside a struct type; instead, pass a Context
explicitly to each function that needs it. The Context should be the first
parameter, typically named ctx:

func DoSomething(ctx context.Context, arg Arg) error {
// ... use ctx ...

Do not pass a nil Context, even if a function permits it. Pass context.TODO
if you are unsure about which Context to use.

Use context Values only for request-scoped data that transits processes and
APIs, not for passing optional parameters to functions.

The same Context may be passed to functions running in different goroutines;
Contexts are safe for simultaneous use by multiple goroutines.

See for example code for a server that uses




Constants are variables with :const true in their metadata. Joker currently does not recognize them as special; as such, it allows redefining them or their values.


Functions, Macros, and Special Forms