refactor: use dependency injection

internal/auth/auth.go

@@ -6,8 +6,18 @@ import (
 	"golang.org/x/crypto/bcrypt"
 )
 
-func FindUser(userList types.UserList, username string) (*types.User) {
-	for _, user := range userList.Users {
+func NewAuth(userList types.Users) *Auth {
+	return &Auth{
+		Users: userList,
+	}
+}
+
+type Auth struct {
+	Users types.Users
+}
+
+func (auth *Auth) GetUser(username string) *types.User {
+	for _, user := range auth.Users {
 		if user.Username == username {
 			return &user
 		}
@@ -15,7 +25,7 @@ func FindUser(userList types.UserList, username string) (*types.User) {
 	return nil
 }
 
-func CheckPassword(user types.User, password string) bool {
+func (auth *Auth) CheckPassword(user types.User, password string) bool {
 	hashedPasswordErr := bcrypt.CompareHashAndPassword([]byte(user.Password), []byte(password))
 	return hashedPasswordErr == nil
 }