// Undetected dead lock.
package main

import (
    "fmt"
    "sync"
    "time"
)

type myType struct {
    mu     sync.Mutex
    kill   chan struct{}
    ticker *time.Ticker
}

func New(interval time.Duration) *myType {
    t := &myType{
        kill:   make(chan struct{}),
        ticker: time.NewTicker(interval),
    }
    go func(m *myType) {
        for {
            select {
            case <-m.kill:
                m.ticker.Stop()
                return
            case <-m.ticker.C:
                fmt.Printf("ticker locking\n")
                m.mu.Lock()
                fmt.Printf("tick\n")
                m.mu.Unlock()
                fmt.Printf("ticker unlocked\n")
            }
        }
    }(t)
    return t
}

func (m *myType) Close() {
    fmt.Printf("closing\n")
    m.mu.Lock()
    m.kill <- struct{}{}
    m.mu.Unlock()
    fmt.Printf("closed\n")
}

func main() {
    // Close acquires the lock but the ticker goroutine gets a ticker event
    // and tries to acquire the lock as well: program uses 100% cpu and is stalled
    // using nanoseconds to emphasize the issue
    // got the issue with tickers using 100ms
    m := New(time.Duration(10) * time.Nanosecond)
    // sleeping for a little while helps on go1.5rc1 in reproducing the problem
    time.Sleep(time.Duration(20) * time.Nanosecond)
    m.Close()
}