### Goroutines
A goroutine is a lightweight thread managed by Go runtime.
func say(s string){
for i := 0; i < 5; i++ {
time.Sleep(100 * time.Millisecond)
fmt.Println(s)
}
}
func main(){
go say("world")
say("hello")
}
### Channels
Channels are a typed conduit through which you can send and receive values with the channel operator
func sum(s []int, c chan int){
sum := 0
for _, v := range s {
sum += v
}
c <- sum
}
func main(){
s := []int{7, 2, 8, -9, 4, 0}
c := make(chan int)
go sum(s[:len(s)/2], c)
go sum(s[len(s)/2:], c)
x, y := <-c, <-c
fmt.Println(x, y, x+y)
}
Buffered Channels
func main(){
ch := make(chan int, 2)
ch <- 1
ch <- 2
fmt.Println(<-ch)
fmt.Println(<-ch)
}
– Range and close
A sender can close a channel to indicate that no more values will sent. Receivers can test whether a channel has been closed by assigning a second parameter to the receive expression: after
func fibonacci(n int, c chan int){
x, y := 0, 1
for i := 0; i < n; i++ {
c <- x
x, y = y, x+y
}
close(c)
}
func main(){
c := make(chan int, 10)
go fibonacci(cap(c), c)
for i := range c{
fmt.Println(i)
}
}
### Select
The select statement lets a goroutine wait on multiple communication operations.
func fibonacci(c, quit chan int){
x, y := 0, 1
for {
select {
case c <- x:
x, y = y, x+y
case <-quit:
fmt.Println("quit")
return
}
}
}
func main(){
c := make(chan int)
quit := make(chan int)
go func(){
for i := 0; i < 10; i++ {
fmt.Println(<-c)
}
quit <- 0
}()
fibonacci(c, quit)
}
Default Selection
func main(){
tick := time.Tick(100 * time.Millisecond)
boom := time.After(500 * time.Millisecond)
for {
select {
case <-tick:
fmt.Println("tick.")
case <-boom:
fmt.Println("BOOM!")
return
default:
fmt.Println(" .")
time.Sleep(50 * time.Millisecond)
}
}
}
– sync.Mutex
type SafeCounter struct {
mu sync.Mutex
v map[string]int
}
func (c *SafeCounter) Inc(key string){
c.mu.Lock()
c.v[key]++
c.mu.Unlock()
}
func(c *SafeCounter) Value(key string) int {
c.mu.Lock()
defer c.mu.Unlock()
return c.v[key]
}
func main(){
c := SafeCounter{v: make(map[string]int)}
for i := 0; i < 1000; i++ {
go c.Inc("somekey")
}
time.Sleep(time.Second)
fmt.Println(c.Value("somekey"))
}
それではEchoでもやりますか
