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										 |  |  | // 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: | 
					
						
							|  |  |  | // | 
					
						
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										 |  |  | //	func DoSomething(ctx context.Context, arg Arg) error { | 
					
						
							|  |  |  | //		// ... use ctx ... | 
					
						
							|  |  |  | //	} | 
					
						
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										 |  |  | // | 
					
						
							|  |  |  | // 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" | 
					
						
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 | 
					
						
							|  |  |  | // 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 | 
					
						
							|  |  |  | } | 
					
						
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 | 
					
						
							|  |  |  | // 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 | 
					
						
							|  |  |  | } |