net/context/context.go

// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Package context defines the Context type, which carries deadlines,
// cancelation signals, and other request-scoped values across API boundaries
// and between processes.
// As of Go 1.7 this package is available in the standard library under the
// name context.  https://golang.org/pkg/context.
//
// Incoming requests to a server should create a Context, and outgoing calls to
// servers should accept a Context. The chain of function calls between must
// propagate the Context, optionally replacing it with a modified copy created
// using WithDeadline, WithTimeout, WithCancel, or WithValue.
//
// Programs that use Contexts should follow these rules to keep interfaces
// consistent across packages and enable static analysis tools to check context
// propagation:
//
// 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 http://blog.golang.org/context for example code for a server that uses
// Contexts.
package context // import "golang.org/x/net/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 Background() Context {
	return background
}

// 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).  TODO is recognized by static analysis tools that determine
// whether Contexts are propagated correctly in a program.
func TODO() Context {
	return todo
}