Goroutine 泄露 - 被遗忘的发送者

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31 // leak is a buggy function. It launches a goroutine that
32 // blocks receiving from a channel. Nothing will ever be
33 // sent on that channel and the channel is never closed so
34 // that goroutine will be blocked forever.
35 func leak() {
36     ch := make(chan int)
37 
38     go func() {
39         val := <-ch
40         fmt.Println("We received a value:", val)
41     }()
42 }

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38 // result wraps the return values from search. It allows us
39 // to pass both values across a single channel.
40 type result struct {
41     record string
42     err    error
43 }
44 
45 // process is the work for the program. It finds a record
46 // then prints it. It fails if it takes more than 100ms.
47 func process(term string) error {
48 
49     // Create a context that will be canceled in 100ms.
50     ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
51     defer cancel()
52 
53     // Make a channel for the goroutine to report its result.
54     ch := make(chan result)
55 
56     // Launch a goroutine to find the record. Create a result
57     // from the returned values to send through the channel.
58     go func() {
59         record, err := search(term)
60         ch <- result{record, err}
61     }()
62 
63     // Block waiting to either receive from the goroutine's
64     // channel or for the context to be canceled.
65     select {
66     case <-ctx.Done():
67         return errors.New("search canceled")
68     case result := <-ch:
69         if result.err != nil {
70             return result.err
71         }
72         fmt.Println("Received:", result.record)
73         return nil
74     }
75 }

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53     // Make a channel for the goroutine to report its result.
54     // Give it capacity so sending doesn't block.
55     ch := make(chan result, 1)