Fix certmagic usage. Fixes joohoi#337

No separate certmagic cache needed. Default config and cache are sufficient
to handle the certificates for the HTTP API.
Updated to certmagic v0.20.

go.mod

@@ -6,7 +6,7 @@ require (
 	github.com/BurntSushi/toml v1.2.1
 	github.com/DATA-DOG/go-sqlmock v1.5.0
 	github.com/ajg/form v1.5.1 // indirect
-	github.com/caddyserver/certmagic v0.17.2
+	github.com/caddyserver/certmagic v0.20.0
 	github.com/erikstmartin/go-testdb v0.0.0-20160219214506-8d10e4a1bae5
 	github.com/fasthttp-contrib/websocket v0.0.0-20160511215533-1f3b11f56072 // indirect
 	github.com/gavv/httpexpect v2.0.0+incompatible
@@ -15,12 +15,13 @@ require (
 	github.com/gorilla/websocket v1.4.2 // indirect
 	github.com/imkira/go-interpol v1.1.0 // indirect
 	github.com/julienschmidt/httprouter v1.3.0
-	github.com/klauspost/cpuid/v2 v2.2.4 // indirect
+	github.com/klauspost/cpuid/v2 v2.2.7 // indirect
 	github.com/lib/pq v1.10.7
+	github.com/libdns/libdns v0.2.2 // indirect
 	github.com/mattn/go-colorable v0.1.12 // indirect
 	github.com/mattn/go-sqlite3 v1.14.16
-	github.com/mholt/acmez v1.1.0
-	github.com/miekg/dns v1.1.51
+	github.com/mholt/acmez v1.2.0
+	github.com/miekg/dns v1.1.58
 	github.com/moul/http2curl v1.0.0 // indirect
 	github.com/rs/cors v1.8.3
 	github.com/sergi/go-diff v1.2.0 // indirect
@@ -30,9 +31,9 @@ require (
 	github.com/yudai/gojsondiff v1.0.0 // indirect
 	github.com/yudai/golcs v0.0.0-20170316035057-ecda9a501e82 // indirect
 	github.com/yudai/pp v2.0.1+incompatible // indirect
-	go.uber.org/atomic v1.10.0 // indirect
-	go.uber.org/multierr v1.9.0 // indirect
-	go.uber.org/zap v1.24.0 // indirect
-	golang.org/x/crypto v0.7.0
-	golang.org/x/mod v0.9.0 // indirect
+	go.uber.org/atomic v1.11.0 // indirect
+	go.uber.org/multierr v1.11.0 // indirect
+	go.uber.org/zap v1.27.0 // indirect
+	golang.org/x/crypto v0.22.0
+	golang.org/x/tools v0.20.0 // indirect
 )