ch1 := make (chan int, 1)
ch2 := make (chan int, 1)

select {
case <-ch1:
    fmt.Println("ch1 pop one element")
case <-ch2:
    fmt.Println("ch2 pop one element")
}

timeout := make (chan bool, 1)
go func() {
    time.Sleep(1e9) // sleep one second
    timeout <- true
}()
ch := make (chan int)
 
select {
case <- ch:
case <- timeout:
    fmt.Println("timeout!")
}

switch marks {
    case 90: grade = "A"
    case 80: grade = "B"
    case 50,60,70 : grade = "C"
    default: grade = "D" 
}
switch {
    case grade == "A" :
        fmt.Printf("Excellent!\n" )     
    case grade == "B", grade == "C" :
        fmt.Printf("Well done\n" )      
    case grade == "D" :
        fmt.Printf("You passed\n" )      
    case grade == "F":
        fmt.Printf("Better try again\n" )
    default:
        fmt.Printf("Invalid grade\n" );
}
switch i := x.(type) {
    case nil:   
        fmt.Printf("type of x :%T",i)                
    case int:   
        fmt.Printf("x is int")                               
    case func(int) float64:
        fmt.Printf("x is func(int)")                      
    case bool, string:
        fmt.Printf("x is bool or string")       
    default:
        fmt.Printf("don't know the type")     
}  

package main
import (
    "fmt"
    "runtime"
    "sync"
)
// Possible worker states.
const (
    Stopped = 0
    Paused  = 1
    Running = 2
)
// Maximum number of workers.
const WorkerCount = 1000
func main() {
    // Launch workers.
    var wg sync.WaitGroup
    wg.Add(WorkerCount + 1)
    workers := make([]chan int, WorkerCount)
    for i := range workers {
        workers[i] = make(chan int, 1)
        go func(i int) {
            worker(i, workers[i])
            wg.Done()
        }(i)
    }
    // Launch controller routine.
    go func() {
        controller(workers)
        wg.Done()
    }()
    // Wait for all goroutines to finish.
    wg.Wait()
}
func worker(id int, ws <-chan int) {
    state := Paused // Begin in the paused state.
    for {
        select {
        case state = <-ws:
            switch state {
            case Stopped:
                fmt.Printf("Worker %d: Stopped\n", id)
                return
            case Running:
                fmt.Printf("Worker %d: Running\n", id)
            case Paused:
                fmt.Printf("Worker %d: Paused\n", id)
            }
        default:
            // We use runtime.Gosched() to prevent a deadlock in this case.
            // It will not be needed of work is performed here which yields
            // to the scheduler.
            runtime.Gosched()
            if state == Paused {
                break
            }
            // Do actual work here.
        }
    }
}
// controller handles the current state of all workers. They can be
// instructed to be either running, paused or stopped entirely.
func controller(workers []chan int) {
    // Start workers
    setState(workers, Running)
    // Pause workers.
    setState(workers, Paused)
    // Unpause workers.
    setState(workers, Running)
    // Shutdown workers.
    setState(workers, Stopped)
}
// setState changes the state of all given workers.
func setState(workers []chan int, state int) {
    for _, w := range workers {
        w <- state
    }
}