This is the v1 version, had the v2 before.

backend/memory/backend.go

@@ -0,0 +1,78 @@
+// A memory backend.
+package memory
+
+import (
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/backend"
+)
+
+type Backend struct {
+	users map[string]*User
+}
+
+func (be *Backend) Login(_ *imap.ConnInfo, username, password string) (backend.User, error) {
+	user, ok := be.users[username]
+	if ok && user.password == password {
+		return user, nil
+	}
+
+	return nil, errors.New("Bad username or password")
+}
+
+func New() *Backend {
+	user := &User{username: "username", password: "password"}
+
+	body := "From: contact@example.org\r\n" +
+		"To: contact@example.org\r\n" +
+		"Subject: A little message, just for you\r\n" +
+		"Date: Wed, 11 May 2016 14:31:59 +0000\r\n" +
+		"Message-ID: <0000000@localhost/>\r\n" +
+		"Content-Type: text/plain\r\n" +
+		"\r\n" +
+		"Hi there :)"
+
+	user.mailboxes = map[string]*Mailbox{
+		"INBOX": {
+			name: "INBOX",
+			user: user,
+			Messages: []*Message{
+				{
+					Uid:   6,
+					Date:  time.Now(),
+					Flags: []string{"\\Seen"},
+					Size:  uint32(len(body)),
+					Body:  []byte(body),
+				},
+			},
+		},
+	}
+
+	return &Backend{
+		users: map[string]*User{user.username: user},
+	}
+}
+
+// NewUser adds a user to the backend.
+func (be *Backend) NewUser(username, password string) (*User, error) {
+	_, ok := be.users[username]
+	if ok {
+		return nil, fmt.Errorf("user %s is already defined.", username)
+	}
+	u := &User{username: username, password: password, mailboxes: make(map[string]*Mailbox)}
+	be.users[username] = u
+	return u, nil
+}
+
+// DeleteUser removes a user from the backend.
+func (be *Backend) DeleteUser(username string) error {
+	_, ok := be.users[username]
+	if !ok {
+		return fmt.Errorf("user %s is not defined.", username)
+	}
+	delete(be.users, username)
+	return nil
+}