Created
November 5, 2019 09:21
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Mutex
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// :collection Essential Go | |
package main | |
import ( | |
"fmt" | |
"sync" | |
"time" | |
) | |
// :show start | |
var cache map[int]int | |
var mu sync.Mutex | |
func expensiveOperation(n int) int { | |
// in real code this operation would be very expensive | |
return n * n | |
} | |
func getCached(n int) int { | |
mu.Lock() | |
v, isCached := cache[n] | |
mu.Unlock() | |
if isCached { | |
return v | |
} | |
v = expensiveOperation(n) | |
mu.Lock() | |
cache[n] = v | |
mu.Unlock() | |
return v | |
} | |
func accessCache() { | |
total := 0 | |
for i := 0; i < 5; i++ { | |
n := getCached(i) | |
total += n | |
} | |
fmt.Printf("total: %d\n", total) | |
} | |
// :show end | |
func main() { | |
// :show start | |
cache = make(map[int]int) | |
go accessCache() | |
accessCache() | |
// :show end | |
// for simplicity of the example | |
// don't use time.Sleep() to coordinate goroutines | |
// in production code | |
time.Sleep(100 * time.Millisecond) | |
} |
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