add auth layer

auth/password.go

@@ -0,0 +1,18 @@
+package auth
+
+import "golang.org/x/crypto/bcrypt"
+
+type PasswordAuth struct {
+	hash []byte
+}
+
+func NewPasswordAuth(hash string) *PasswordAuth {
+	return &PasswordAuth{hash: []byte(hash)}
+}
+
+func (p *PasswordAuth) Authenticate(_, pass string) error {
+	if err := bcrypt.CompareHashAndPassword(p.hash, []byte(pass)); err != nil {
+		return ErrAuthFailed
+	}
+	return nil
+}