Non-JSON log line "remote error: tls: unknown certificate"

The following are the logs I'm seeing from the prometheus exporter I've built. The last line happens when I launch the landing page/url in my browser. The cert is self-signed so I expect it to maybe warn, but I certainly don't expect it to be non-JSON as I'm passing my logger in and it uses JSON.

	if err := web.ListenAndServe(&http.Server{}, &web.FlagConfig{
		WebListenAddresses: &[]string{server.webListenAddress},
		WebConfigFile:      &server.configFile,
	}, log.Logger); err != nil {
		log.Error(fmt.Sprintf("Error starting web server: %s", err.Error()))
		os.Exit(1)
	}

❯ go run -ldflags="-X main.version=$(cat VERSION) -X main.commit=$(git rev-parse HEAD)" main.go --controller-address http://anka.controller:8090 -web.config.file web.config.yml
{"time":"2024-09-17T20:42:55.378809-05:00","level":"INFO","msg":"Starting Prometheus Exporter for Anka (3.0.1)"}
{"time":"2024-09-17T20:42:55.443433-05:00","level":"INFO","msg":"Serving metrics at :2112/metrics"}
{"time":"2024-09-17T20:42:55.443825-05:00","level":"INFO","msg":"Listening on","address":"[::]:2112"}
{"time":"2024-09-17T20:42:55.444787-05:00","level":"INFO","msg":"TLS is enabled.","http2":true,"address":"[::]:2112"}
2024/09/17 20:43:53 http: TLS handshake error from 127.0.0.1:54574: remote error: tls: unknown certificate

I'm having trouble finding where this comes from though. It seems to be generated from something not using the logger I passed in.

Any recommendations?

Start at the web.ListenAndServe call and the supplied log.Logger integration, then reproduce the self-signed-certificate request shown in the report. Trace where the TLS handshake error is emitted and determine whether it can use the configured logger. Done means the handshake error is emitted in the expected JSON format without changing the reported server behavior.