README
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Context
Context manager package for A-Novel apps.
go get -u github.com/a-novel-kit/context
Documentation
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Index ¶
- Variables
- func AfterFunc(ctx Context, f func()) func() bool
- func Cause(ctx Context) error
- func ExtractValue[T any](ctx context.Context, key any) (T, error)
- func WithCancel(parent Context) (Context, CancelFunc)
- func WithCancelCause(parent Context) (Context, CancelCauseFunc)
- func WithDeadline(parent Context, deadline time.Time) (Context, CancelFunc)
- func WithDeadlineCause(parent Context, deadline time.Time, cause error) (Context, CancelFunc)
- func WithTimeout(parent Context, timeout time.Duration) (Context, CancelFunc)
- func WithTimeoutCause(parent Context, timeout time.Duration, cause error) (Context, CancelFunc)
- type CancelCauseFunc
- type CancelFunc
- type Context
Constants ¶
This section is empty.
Variables ¶
var Canceled = context.Canceled
Canceled is the error returned by Context.Err when the context is canceled.
var DeadlineExceeded = context.DeadlineExceeded
DeadlineExceeded is the error returned by Context.Err when the context's deadline passes.
var ErrUnsupportedContext = errors.New("unsupported context")
Functions ¶
func AfterFunc ¶
AfterFunc arranges to call f in its own goroutine after ctx is done (canceled or timed out). If ctx is already done, AfterFunc calls f immediately in its own goroutine.
Multiple calls to AfterFunc on a context operate independently; one does not replace another.
Calling the returned stop function stops the association of ctx with f. It returns true if the call stopped f from being run. If stop returns false, either the context is done and f has been started in its own goroutine; or f was already stopped. The stop function does not wait for f to complete before returning. If the caller needs to know whether f is completed, it must coordinate with f explicitly.
If ctx has a "AfterFunc(func()) func() bool" method, AfterFunc will use it to schedule the call.
func Cause ¶
Cause returns a non-nil error explaining why c was canceled. The first cancellation of c or one of its parents sets the cause. If that cancellation happened via a call to CancelCauseFunc(err), then Cause returns err. Otherwise Cause(c) returns the same value as c.Err(). Cause returns nil if c has not been canceled yet.
func ExtractValue ¶
ExtractValue extracts a value from a context with the correct typing, It fails if the value is missing or has the wrong type.
func WithCancel ¶
func WithCancel(parent Context) (Context, CancelFunc)
WithCancel returns a copy of parent with a new Done channel. The returned context's Done channel is closed when the returned cancel function is called or when the parent context's Done channel is closed, whichever happens first.
Canceling this context releases resources associated with it, so code should call cancel as soon as the operations running in this Context complete.
func WithCancelCause ¶
func WithCancelCause(parent Context) (Context, CancelCauseFunc)
WithCancelCause behaves like WithCancel but returns a CancelCauseFunc instead of a CancelFunc. Calling cancel with a non-nil error (the "cause") records that error in ctx; it can then be retrieved using Cause(ctx). Calling cancel with nil sets the cause to Canceled.
Example use:
ctx, cancel := context.WithCancelCause(parent) cancel(myError) ctx.Err() // returns context.Canceled context.Cause(ctx) // returns myError
func WithDeadline ¶
func WithDeadline(parent Context, deadline time.Time) (Context, CancelFunc)
WithDeadline returns a copy of the parent context with the deadline adjusted to be no later than d. If the parent's deadline is already earlier than d, WithDeadline(parent, d) is semantically equivalent to parent. The returned [Context.Done] channel is closed when the deadline expires, when the returned cancel function is called, or when the parent context's Done channel is closed, whichever happens first.
Canceling this context releases resources associated with it, so code should call cancel as soon as the operations running in this Context complete.
func WithDeadlineCause ¶
WithDeadlineCause behaves like WithDeadline but also sets the cause of the returned Context when the deadline is exceeded. The returned CancelFunc does not set the cause.
func WithTimeout ¶
func WithTimeout(parent Context, timeout time.Duration) (Context, CancelFunc)
WithTimeout returns WithDeadline(parent, time.Now().Add(timeout)).
Canceling this context releases resources associated with it, so code should call cancel as soon as the operations running in this Context complete:
func slowOperationWithTimeout(ctx context.Context) (Result, error) {
ctx, cancel := context.WithTimeout(ctx, 100*time.Millisecond)
defer cancel() // releases resources if slowOperation completes before timeout elapses
return slowOperation(ctx)
}
func WithTimeoutCause ¶
WithTimeoutCause behaves like WithTimeout but also sets the cause of the returned Context when the timeout expires. The returned CancelFunc does not set the cause.
Types ¶
type CancelCauseFunc ¶
type CancelCauseFunc = context.CancelCauseFunc
A CancelCauseFunc behaves like a CancelFunc but additionally sets the cancellation cause. This cause can be retrieved by calling Cause on the canceled Context or on any of its derived Contexts.
If the context has already been canceled, CancelCauseFunc does not set the cause. For example, if childContext is derived from parentContext:
- if parentContext is canceled with cause1 before childContext is canceled with cause2, then Cause(parentContext) == Cause(childContext) == cause1
- if childContext is canceled with cause2 before parentContext is canceled with cause1, then Cause(parentContext) == cause1 and Cause(childContext) == cause2
type CancelFunc ¶
type CancelFunc = context.CancelFunc
A CancelFunc tells an operation to abandon its work. A CancelFunc does not wait for the work to stop. A CancelFunc may be called by multiple goroutines simultaneously. After the first call, subsequent calls to a CancelFunc do nothing.
type Context ¶
A Context carries a deadline, a cancellation signal, and other values across API boundaries.
Context's methods may be called by multiple goroutines simultaneously.
func Background ¶
func Background() Context
Background returns a non-nil, empty Context. It is never canceled, has no values, and has no deadline. It is typically used by the main function, initialization, and tests, and as the top-level Context for incoming requests.
func TODO ¶
func TODO() Context
TODO returns a non-nil, empty Context. Code should use context.TODO when it's unclear which Context to use or it is not yet available (because the surrounding function has not yet been extended to accept a Context parameter).
func WithValue ¶
WithValue returns a copy of parent in which the value associated with key is val.
Use context Values only for request-scoped data that transits processes and APIs, not for passing optional parameters to functions.
The provided key must be comparable and should not be of type string or any other built-in type to avoid collisions between packages using context. Users of WithValue should define their own types for keys. To avoid allocating when assigning to an interface{}, context keys often have concrete type struct{}. Alternatively, exported context key variables' static type should be a pointer or interface.
func WithoutCancel ¶
WithoutCancel returns a copy of parent that is not canceled when parent is canceled. The returned context returns no Deadline or Err, and its Done channel is nil. Calling Cause on the returned context returns nil.
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