hook.service causes panic on shutdown

[tobya]

if hook.service is build into caddy using current master if caddy is run from command line in windows and then stopped by ctrl-c the following panic happens

panic: close of closed channel

goroutine 81 [running]:
github.com/mholt/caddy/vendor/github.com/mholt/certmagic.(*Cache).Stop(...)
        D:/godev/src/github.com/mholt/caddy/vendor/github.com/mholt/certmagic/cache.go:87
github.com/mholt/caddy/caddytls.NewConfig.func1(0x10694f0, 0xc0420cc340)
        D:/godev/src/github.com/mholt/caddy/caddytls/config.go:105 +0x35
github.com/mholt/caddy.(*Instance).ShutdownCallbacks(0xc04223c000, 0xc0420cc340, 0xc0420cc340, 0x0)
        D:/godev/src/github.com/mholt/caddy/caddy.go:169 +0xba
github.com/mholt/caddy.allShutdownCallbacks(0xbf02d0, 0x8, 0xad3bc0)
        D:/godev/src/github.com/mholt/caddy/sigtrap.go:100 +0x114
github.com/mholt/caddy.executeShutdownCallbacks.func1()
        D:/godev/src/github.com/mholt/caddy/sigtrap.go:80 +0x96
sync.(*Once).Do(0x1097820, 0xc042007f88)
        C:/Go/src/sync/once.go:44 +0xc5
github.com/mholt/caddy.executeShutdownCallbacks(0xbed72f, 0x6, 0x0)
        D:/godev/src/github.com/mholt/caddy/sigtrap.go:76 +0x7a
github.com/mholt/caddy.trapSignalsCrossPlatform.func1.1()
        D:/godev/src/github.com/mholt/caddy/sigtrap.go:66 +0x3d
created by github.com/mholt/caddy.trapSignalsCrossPlatform.func1
        D:/godev/src/github.com/mholt/caddy/sigtrap.go:65 +0xe3

In discussion @mholt thought perhaps

It looks like they're calling ShutdownCallbacks too, but the Ctrl+c handler does this already

[hacdias]

Hmm... we do call ShutdownCallbacks when stopping the service. We call that and instance.Stop. Shouldn't we?

/cc @mholt

[mholt]

No, I don't believe so. The caddy package does that already. https://sourcegraph.com/github.com/mholt/caddy@a2ed91bc45c8b3faa1577ed4c18334d38a581ca7/-/blob/sigtrap.go#L66

[hacdias]

@mholt hmmm... it does that when signals are emitted. What about services shutting down? I'm not sure how they work and if there's a signal being emitted. I can try removing them and see what happens tho.

[mholt]

Yeah... sorry, it is a little confusing in this case because of the whole service paradigm.

Some service managers like systemd send a signal to shut down the process, making these calls redundant. (I'm not sure what Windows does.)

[hacdias]

Due to the recent developments of Caddy (v2!) and the incompatibility of this plugin with newer versions, as well as not being maintained, I'm closing this issue and archiving the repository.