github.com/graybobo/golang.org-package-offline-cache@v0.0.0-20200626051047-6608995c132f/x/talks/2012/concurrency/support/sequenceboring.go (about)

     1  // +build OMIT
     2  
     3  package main
     4  
     5  import (
     6  	"fmt"
     7  	"math/rand"
     8  	"time"
     9  )
    10  
    11  // START0 OMIT
    12  type Message struct {
    13  	str string
    14  	wait chan bool // HL
    15  }
    16  // STOP0 OMIT
    17  
    18  func main() {
    19  	c := fanIn(boring("Joe"), boring("Ann")) // HL
    20  // START1 OMIT
    21  	for i := 0; i < 5; i++ {
    22  		msg1 := <-c; fmt.Println(msg1.str)
    23  		msg2 := <-c; fmt.Println(msg2.str)
    24  		msg1.wait <- true
    25  		msg2.wait <- true
    26  	}
    27  // STOP1 OMIT
    28  	fmt.Println("You're all boring; I'm leaving.")
    29  }
    30  
    31  func boring(msg string) <-chan Message { // Returns receive-only channel of strings. // HL
    32  	c := make(chan Message)
    33  // START2 OMIT
    34  	waitForIt := make(chan bool) // Shared between all messages.
    35  // STOP2 OMIT
    36  	go func() { // We launch the goroutine from inside the function. // HL
    37  		for i := 0; ; i++ {
    38  // START3 OMIT
    39  			c <- Message{ fmt.Sprintf("%s: %d", msg, i), waitForIt }
    40  			time.Sleep(time.Duration(rand.Intn(2e3)) * time.Millisecond)
    41  			<-waitForIt
    42  // STOP3 OMIT
    43  		}
    44  	}()
    45  	return c // Return the channel to the caller. // HL
    46  }
    47  
    48  
    49  // START3 OMIT
    50  func fanIn(inputs ... <-chan Message) <-chan Message { // HL
    51  	c := make(chan Message)
    52  	for i := range inputs {
    53  		input := inputs[i] // New instance of 'input' for each loop.
    54  		go func() { for { c <- <-input } }()
    55  	}
    56  	return c
    57  }
    58  // STOP3 OMIT