cmd: use automaxprocs for better perf in containers (#5711)

* feat: use automaxprocs for better perf in containers

* better logs

* cs

cmd/caddy/main.go

@@ -29,12 +29,22 @@
 package main
 
 import (
+	"go.uber.org/automaxprocs/maxprocs"
+	"go.uber.org/zap"
+
 	caddycmd "github.com/caddyserver/caddy/v2/cmd"
 
+	"github.com/caddyserver/caddy/v2"
 	// plug in Caddy modules here
 	_ "github.com/caddyserver/caddy/v2/modules/standard"
 )
 
 func main() {
+	undo, err := maxprocs.Set()
+	defer undo()
+	if err != nil {
+		caddy.Log().Warn("failed to set GOMAXPROCS", zap.Error(err))
+	}
+
 	caddycmd.Main()
 }