Add support for running profiling when debug build-tags provided (#491)

* wrap root HTTP handler in debug.WithPprof(), rearrange router.Start() to support this
* remove unused code
* set debug buildtag in build script when $DEBUG set
* update go-debug version with fixed handler
* use clone of router.srv for LE cert manager, reset server timeouts in debug
* add kim's other libraries to README

vendor/codeberg.org/gruf/go-debug/pprof_on.go

@@ -0,0 +1,63 @@
+//go:build debug || debugenv
+// +build debug debugenv
+
+package debug
+
+import (
+	"net/http"
+	"net/http/pprof"
+	"strings"
+)
+
+// ServePprof will start an HTTP server serving /debug/pprof only if debug enabled.
+func ServePprof(addr string) error {
+	if !debug {
+		// debug disabled in env
+		return nil
+	}
+	handler := WithPprof(nil)
+	return http.ListenAndServe(addr, handler)
+}
+
+// WithPprof will add /debug/pprof handling (provided by "net/http/pprof") only if debug enabled.
+func WithPprof(handler http.Handler) http.Handler {
+	if !debug {
+		// debug disabled in env
+		return handler
+	}
+
+	// Default serve mux is setup with pprof
+	pprofmux := http.DefaultServeMux
+
+	if pprofmux == nil {
+		// Someone nil'ed the default mux
+		pprofmux = &http.ServeMux{}
+		pprofmux.HandleFunc("/debug/pprof/", pprof.Index)
+		pprofmux.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
+		pprofmux.HandleFunc("/debug/pprof/profile", pprof.Profile)
+		pprofmux.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
+		pprofmux.HandleFunc("/debug/pprof/trace", pprof.Trace)
+	}
+
+	if handler == nil {
+		// Ensure handler is non-nil
+		handler = http.NotFoundHandler()
+	}
+
+	// Debug enabled, return wrapped handler func
+	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+		const prefix = "/debug/pprof"
+
+		// /debug/pprof(/.*)? -> pass to pprofmux
+		if strings.HasPrefix(r.URL.Path, prefix) {
+			path := r.URL.Path[len(prefix):]
+			if path == "" || path[0] == '/' {
+				pprofmux.ServeHTTP(rw, r)
+				return
+			}
+		}
+
+		// .* -> pass to handler
+		handler.ServeHTTP(rw, r)
+	})
+}