For the following code:

func ExampleCond_single() {
    var m Mutex
    c := MakeCond(&m)
    percent := 0
    const step = 10
    for i := 0; i < 5; i++ {
        go func() {       // ######## LINE 134
            for {
                // Emulates some useful work.
                time.Sleep(1e8)
                m.Lock()
                defer    // ######## The problem is actually here
                if percent == 100 {
                    m.Unlock()
                    break
                }
                percent++
                if percent % step == 0 {
                    c.Signal()
                }
                m.Unlock()
            }
        }()
    }
    for {
        m.Lock()
        if percent == 0 || percent % step != 0 {
            c.Wait()
        }
        fmt.Print(",")
        if percent == 100 {
            m.Unlock()
            break
        }
        m.Unlock()
    }
}

gc says only:
cond_test.go:134:6: expected function/method call (and 14 more errors)

This usually means then I miss "()" after "go func() {}", but it is
not the case here. It confuses. The problem is actually with stand-alone defer.

12079:45a0ca092e9d tip