1 // Copyright 2014 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
5 // Package context defines the Context type, which carries deadlines,
6 // cancelation signals, and other request-scoped values across API boundaries
7 // and between processes.
8 // As of Go 1.7 this package is available in the standard library under the
9 // name context. https://golang.org/pkg/context.
11 // Incoming requests to a server should create a Context, and outgoing calls to
12 // servers should accept a Context. The chain of function calls between must
13 // propagate the Context, optionally replacing it with a modified copy created
14 // using WithDeadline, WithTimeout, WithCancel, or WithValue.
16 // Programs that use Contexts should follow these rules to keep interfaces
17 // consistent across packages and enable static analysis tools to check context
20 // Do not store Contexts inside a struct type; instead, pass a Context
21 // explicitly to each function that needs it. The Context should be the first
22 // parameter, typically named ctx:
24 // func DoSomething(ctx context.Context, arg Arg) error {
28 // Do not pass a nil Context, even if a function permits it. Pass context.TODO
29 // if you are unsure about which Context to use.
31 // Use context Values only for request-scoped data that transits processes and
32 // APIs, not for passing optional parameters to functions.
34 // The same Context may be passed to functions running in different goroutines;
35 // Contexts are safe for simultaneous use by multiple goroutines.
37 // See http://blog.golang.org/context for example code for a server that uses
39 package context // import "golang.org/x/net/context"
41 // Background returns a non-nil, empty Context. It is never canceled, has no
42 // values, and has no deadline. It is typically used by the main function,
43 // initialization, and tests, and as the top-level Context for incoming
45 func Background() Context {
49 // TODO returns a non-nil, empty Context. Code should use context.TODO when
50 // it's unclear which Context to use or it is not yet available (because the
51 // surrounding function has not yet been extended to accept a Context
52 // parameter). TODO is recognized by static analysis tools that determine
53 // whether Contexts are propagated correctly in a program.