Data commit

Task/Mutex/Go/mutex-1.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+    "fmt"
+    "sync"
+    "time"
+)
+
+var value int
+var m sync.Mutex
+var wg sync.WaitGroup
+
+func slowInc() {
+    m.Lock()
+    v := value
+    time.Sleep(1e8)
+    value = v+1
+    m.Unlock()
+    wg.Done()
+}
+
+func main() {
+    wg.Add(2)
+    go slowInc()
+    go slowInc()
+    wg.Wait()
+    fmt.Println(value)
+}

Task/Mutex/Go/mutex-2.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+    "fmt"
+    "time"
+)
+
+var value int
+
+func slowInc(ch, done chan bool) {
+    // channel receive, used here to implement mutex lock.
+    // it will block until a value is available on the channel
+    <-ch
+
+    // same as above
+    v := value
+    time.Sleep(1e8)
+    value = v + 1
+
+    // channel send, equivalent to mutex unlock.
+    // makes a value available on channel
+    ch <- true
+
+    // channels can be used to signal completion too
+    done <- true
+}
+
+func main() {
+    ch := make(chan bool, 1) // ch used as a mutex
+    done := make(chan bool)  // another channel used to signal completion
+    go slowInc(ch, done)
+    go slowInc(ch, done)
+    // a freshly created sync.Mutex starts out unlocked, but a freshly created
+    // channel is empty, which for us represents "locked."  sending a value on
+    // the channel puts the value up for grabs, thus representing "unlocked."
+    ch <- true
+    <-done
+    <-done
+    fmt.Println(value)
+}