context

README

Context

Context is api-compatible with go 1.7's context package, and with the older golang.org/x/net/context package. It uses build flags to control which backing context implementation it uses. On go 1.7, it will delegate to the package in the SDK. On earlier versions of go, it will use the golang.org/x/net/context package.

Documentation

Index

• Variables
• func WithCancel(parent Context) (ctx Context, cancel CancelFunc)
• func WithDeadline(parent Context, deadline time.Time) (Context, CancelFunc)
• func WithTimeout(parent Context, timeout time.Duration) (Context, CancelFunc)
• type CancelFunc
• type Context
  • func Background() Context
  • func TODO() Context
  • func WithValue(parent Context, key, val interface{}) Context

Variables

var Canceled = context.Canceled

var DeadlineExceeded = context.DeadlineExceeded

Functions

func WithCancel

func WithCancel(parent Context) (ctx Context, cancel CancelFunc)

func WithDeadline

func WithDeadline(parent Context, deadline time.Time) (Context, CancelFunc)

func WithTimeout

func WithTimeout(parent Context, timeout time.Duration) (Context, CancelFunc)

Types

type CancelFunc

type CancelFunc func()

type Context

type Context interface {
	// Deadline returns the time when work done on behalf of this context
	// should be canceled. Deadline returns ok==false when no deadline is
	// set. Successive calls to Deadline return the same results.
	Deadline() (deadline time.Time, ok bool)

	// Done returns a channel that's closed when work done on behalf of this
	// context should be canceled. Done may return nil if this context can
	// never be canceled. Successive calls to Done return the same value.
	//
	// WithCancel arranges for Done to be closed when cancel is called;
	// WithDeadline arranges for Done to be closed when the deadline
	// expires; WithTimeout arranges for Done to be closed when the timeout
	// elapses.
	//
	// Done is provided for use in select statements:
	//
	//  // Stream generates values with DoSomething and sends them to out
	//  // until DoSomething returns an error or ctx.Done is closed.
	//  func Stream(ctx context.Context, out chan<- Value) error {
	//  	for {
	//  		v, err := DoSomething(ctx)
	//  		if err != nil {
	//  			return err
	//  		}
	//  		select {
	//  		case <-ctx.Done():
	//  			return ctx.Err()
	//  		case out <- v:
	//  		}
	//  	}
	//  }
	//
	// See https://blog.golang.org/pipelines for more examples of how to use
	// a Done channel for cancelation.
	Done() <-chan struct{}

	// Err returns a non-nil error value after Done is closed. Err returns
	// Canceled if the context was canceled or DeadlineExceeded if the
	// context's deadline passed. No other values for Err are defined.
	// After Done is closed, successive calls to Err return the same value.
	Err() error

	// Value returns the value associated with this context for key, or nil
	// if no value is associated with key. Successive calls to Value with
	// the same key returns the same result.
	//
	// Use context values only for request-scoped data that transits
	// processes and API boundaries, not for passing optional parameters to
	// functions.
	//
	// A key identifies a specific value in a Context. Functions that wish
	// to store values in Context typically allocate a key in a global
	// variable then use that key as the argument to context.WithValue and
	// Context.Value. A key can be any type that supports equality;
	// packages should define keys as an unexported type to avoid
	// collisions.
	//
	// Packages that define a Context key should provide type-safe accessors
	// for the values stored using that key:
	//
	// 	// Package user defines a User type that's stored in Contexts.
	// 	package user
	//
	// 	import "context"
	//
	// 	// User is the type of value stored in the Contexts.
	// 	type User struct {...}
	//
	// 	// key is an unexported type for keys defined in this package.
	// 	// This prevents collisions with keys defined in other packages.
	// 	type key int
	//
	// 	// userKey is the key for user.User values in Contexts. It is
	// 	// unexported; clients use user.NewContext and user.FromContext
	// 	// instead of using this key directly.
	// 	var userKey key = 0
	//
	// 	// NewContext returns a new Context that carries value u.
	// 	func NewContext(ctx context.Context, u *User) context.Context {
	// 		return context.WithValue(ctx, userKey, u)
	// 	}
	//
	// 	// FromContext returns the User value stored in ctx, if any.
	// 	func FromContext(ctx context.Context) (*User, bool) {
	// 		u, ok := ctx.Value(userKey).(*User)
	// 		return u, ok
	// 	}
	Value(key interface{}) interface{}
}

copied from 1.7 SDK context package

func Background

func Background() Context

func TODO

func TODO() Context

func WithValue

func WithValue(parent Context, key, val interface{}) Context