How to close and cancel pipeline operations using pipeline in Go language?

In Go, closing the pipeline will send an implicit value nil, indicating that subsequent sending fails; while canceling the pipeline operation, use context.WithCancel() to create a context with cancellation function, and call the cancel() function to cancel the operation, resulting in The pipeline operation exited.

Pipeline closing and canceling operations in Go language

Pipelines are an important tool for concurrent programming in Go language. It is critical to understand and correctly use the pipe's close and cancel functions.

Pipe Closure

After sending all necessary data to the pipe, you can call the close(ch) function to close the pipe. This will send an implicit value nil to the pipe, indicating that subsequent sends will fail.

package main

import "fmt"

func main() {
  ch := make(chan int)
  
  go func() {
    // 发送一些值
    ch <- 1
    ch <- 2
    
    // 关闭管道
    close(ch)
  }()
  
  // 接收管道中的值
  for v := range ch {
    fmt.Println(v)
  }
  
  // Pipline 已经关闭，接收操作将会退出并打印 "<nil>"
  fmt.Println(<-ch)
}

Cancel Pipe Operation

In some cases, it may be necessary to cancel a pipeline operation without waiting for all data to be sent and received. A context with cancellation functionality can be created using the context.WithCancel() function.

package main

import (
  "context"
  "fmt"
)

func main() {
  ctx, cancel := context.WithCancel(context.Background())
  
  ch := make(chan int)
  
  go func() {
    // 发送一些值
    for i := 0; i < 5; i++ {
      select {
        case <-ctx.Done():
          return
        case ch <- i:
      }
    }
  }()
  
  // 取消管道操作
  cancel()
  
  // 接收管道中的值
  for v := range ch {
    fmt.Println(v)
  }
}

In the above example, calling the cancel() function will cancel the context, causing the pipeline operation to exit. Note that the pipeline needs to be synchronized with the coroutine that operates on it to ensure that all ongoing operations handle cancellation correctly.

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