go-concurrency-talk/examples/rwmutex.go

55 lines
949 B
Go

package main
import (
"fmt"
"sync"
)
// START OMIT
// SafeCounter is safe to use concurrently.
type SafeCounter struct {
v map[string]int
mux sync.RWMutex
}
// Inc increments the counter for the given key.
func (c *SafeCounter) Inc(key string) {
c.mux.Lock()
// Lock so only one goroutine at a time can access the map.
defer c.mux.Unlock()
c.v[key]++
}
// Value returns the current value of the counter for the given key.
func (c *SafeCounter) Value(key string) int {
c.mux.RLock()
// Many readers can get this lock at once, but Lock() takes priority.
defer c.mux.RUnlock()
return c.v[key]
}
//END OMIT
func main() {
c := &SafeCounter{v: make(map[string]int)}
s := sync.WaitGroup{}
s.Add(3)
go func() {
c.Inc("key")
fmt.Println(c.Value("key"))
s.Done()
}()
go func() {
c.Inc("key")
fmt.Println(c.Value("key"))
s.Done()
}()
go func() {
c.Inc("key")
fmt.Println(c.Value("key"))
s.Done()
}()
s.Wait()
}