refactor out into packages for easier unit test writing

pkg/app/dns/dns.go

@@ -0,0 +1,37 @@
+package app_dns
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/http"
+	"strings"
+
+	"github.com/go-chi/chi"
+)
+
+type app struct {
+	resolver *net.Resolver
+}
+
+func New(ctx context.Context) *app {
+	return &app{resolver: net.DefaultResolver}
+}
+func (app *app) getDNS(w http.ResponseWriter, r *http.Request) {
+	domain := chi.URLParam(r, "domain")
+
+	w.Header().Set("Content-Type", "text/plain")
+
+	res, err := app.resolver.LookupTXT(r.Context(), domain)
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+
+		fmt.Fprintln(w, err)
+		return
+	}
+
+	fmt.Fprintln(w, strings.Join(res, "\n"))
+}
+func (app *app) Routes(r *chi.Mux) {
+	r.MethodFunc("GET", "/dns/{domain}", app.getDNS)
+}