'panic: close of closed channel' using simple example code

[christophershirk]

What version of the package are you using?

v0.10.7

What are you trying to do?

Run example code

import (
        "net/http"
        "github.com/caddyserver/certmagic"
        "fmt"
        "log"

)


func main() {
        http.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
                fmt.Fprintf(w, "Hello world")
        })

        err := certmagic.HTTPS([]string{"tmp.mydomain.com"}, nil)
        if err != nil {
                log.Fatal(err)
        }
}

What steps did you take?

1. On tmp.mydomain.com server, removed .local/share/certmagic directory (to start fresh)
2. Built code locally, scp'd to tmp.mydomain.com
3. On tmp.mydomain.com, performed: setcap 'cap_net_bind_service=+ep' ./autotest3 && ./autotest3

What did you expect to happen, and what actually happened instead?

Sometimes the example code works, sometimes it panics like this:

2020/04/05 00:21:57 [INFO][tmp.mydomain.com] Obtain certificate; acquiring lock...
2020/04/05 00:21:57 [INFO][tmp.mydomain.com] Obtain: Lock acquired; proceeding...
2020/04/05 00:21:57 [INFO] acme: Registering account for dude@mydomain.com
2020/04/05 00:21:57 [INFO][tmp.mydomain.com] Waiting on rate limiter...
2020/04/05 00:21:57 [INFO][tmp.mydomain.com] Done waiting
2020/04/05 00:21:57 [INFO] [tmp.mydomain.com] acme: Obtaining bundled SAN certificate given a CSR
2020/04/05 00:21:57 [INFO] [tmp.mydomain.com] AuthURL: https://acme-v02.api.letsencrypt.org/acme/authz-v3/3765978543
2020/04/05 00:21:57 [INFO] [tmp.mydomain.com] acme: use tls-alpn-01 solver
2020/04/05 00:21:57 [INFO] [tmp.mydomain.com] acme: Trying to solve TLS-ALPN-01
2020/04/05 00:21:58 [INFO][tmp.mydomain.com] Served key authentication certificate (TLS-ALPN challenge)
2020/04/05 00:21:58 [INFO][tmp.mydomain.com] Served key authentication certificate (TLS-ALPN challenge)
2020/04/05 00:21:58 [INFO][tmp.mydomain.com] Served key authentication certificate (TLS-ALPN challenge)
2020/04/05 00:21:58 [INFO][tmp.mydomain.com] Served key authentication certificate (TLS-ALPN challenge)
2020/04/05 00:22:04 [INFO] [tmp.mydomain.com] The server validated our request
panic: close of closed channel
        panic: close of closed channel
        panic: close of closed channel
        panic: close of closed channel

goroutine 29 [running]:
github.com/caddyserver/certmagic.(*tlsALPNSolver).Present.func1(0xc0000f5da0, 0xc000326cc0)
        /home/x/go/pkg/mod/github.com/caddyserver/certmagic@v0.10.7/solvers.go:155 +0x177
created by github.com/caddyserver/certmagic.(*tlsALPNSolver).Present
        /home/x/go/pkg/mod/github.com/caddyserver/certmagic@v0.10.7/solvers.go:149 +0x709

How do you think this should be fixed?

Out of curiosity, I built the code both with the datarace detector enabled and disabled, and I can reproduce the issue (intermittently) in both cases.

[mholt]

Thanks for the report, but this is fixed already. 😃 Simply upgrade to the latest version.