Acquire the database connection in App.ServeHTTP with cookie set

Almost all request will need the database connection, either because
they will perform queries or because they need to check if the user is
logged in, for instance, so it should be acquired as far above as
possible to avoid acquiring multiple connections.

This is specially true since i have to pass the cookie to the database
to switch role and set request.user.email and request.user.cookie
config variables.  I do not want to do that many times per request.

pkg/app/app.go

@@ -57,16 +57,22 @@ func New(db *database.DB) http.Handler {
 func (h *App) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	var head string
 	head, r.URL.Path = shiftPath(r.URL.Path)
-	switch head {
+	if head == "static" {
-	case "static":
 		h.fileHandler.ServeHTTP(w, r)
-	case "login":
+	} else {
+		cookie := getSessionCookie(r)
+		conn := h.db.MustAcquire(r.Context(), cookie)
+		defer conn.Release()
+
+		if head == "login" {
 			switch r.Method {
 			case http.MethodPost:
-			h.handleLogin(w, r)
+				h.handleLogin(w, r, conn)
 			default:
 				methodNotAllowed(w, r, http.MethodPost)
 			}
+		} else {
+			switch head {
 			case "":
 				switch r.Method {
 				case http.MethodGet:
@@ -77,4 +83,6 @@ func (h *App) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 			default:
 				http.NotFound(w, r)
 			}
+		}
+	}
 }

pkg/app/login.go

@@ -10,6 +10,7 @@ import (
 	"net/http"
 	"time"
 
+	"dev.tandem.ws/tandem/camper/pkg/database"
 	"dev.tandem.ws/tandem/camper/pkg/form"
 	httplib "dev.tandem.ws/tandem/camper/pkg/http"
 	"dev.tandem.ws/tandem/camper/pkg/locale"
@@ -65,7 +66,7 @@ func (h *App) matchLocale(r *http.Request) *locale.Locale {
 	return locale.Match(r, h.locales, h.defaultLocale, h.languageMatcher)
 }
 
-func (h *App) handleLogin(w http.ResponseWriter, r *http.Request) {
+func (h *App) handleLogin(w http.ResponseWriter, r *http.Request, conn *database.Conn) {
 	login := newLoginForm()
 	if err := login.Parse(r); err != nil {
 		http.Error(w, err.Error(), http.StatusBadRequest)
@@ -73,7 +74,6 @@ func (h *App) handleLogin(w http.ResponseWriter, r *http.Request) {
 	}
 	l := h.matchLocale(r)
 	if login.Valid(l) {
-		conn := h.db.MustAcquire(r.Context())
 		cookie := conn.MustGetText(r.Context(), "select login($1, $2, $3)", login.Email, login.Password, httplib.RemoteAddr(r))
 		if cookie != "" {
 			setSessionCookie(w, cookie)
@@ -92,6 +92,13 @@ func setSessionCookie(w http.ResponseWriter, cookie string) {
 	http.SetCookie(w, createSessionCookie(cookie, 8766*24*time.Hour))
 }
 
+func getSessionCookie(r *http.Request) string {
+	if cookie, err := r.Cookie(sessionCookie); err == nil {
+		return cookie.Value
+	}
+	return ""
+}
+
 func createSessionCookie(value string, duration time.Duration) *http.Cookie {
 	return &http.Cookie{
 		Name:     sessionCookie,

pkg/database/db.go

@@ -53,11 +53,14 @@ func (db *DB) Acquire(ctx context.Context) (*Conn, error) {
 	return &Conn{conn}, nil
 }
 
-func (db *DB) MustAcquire(ctx context.Context) *Conn {
+func (db *DB) MustAcquire(ctx context.Context, cookie string) *Conn {
 	conn, err := db.Acquire(ctx)
 	if err != nil {
 		panic(err)
 	}
+	if _, err = conn.Exec(ctx, "select set_cookie($1)", cookie); err != nil {
+		panic(false)
+	}
 	return conn
 }