Multi DB API (#164)

* Multi DB API

* Updated changelog

Author: hiranya911

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Unreleased
 
+- [added] `firebase.App` now provides a new `DatabaseWithURL()` function
+  for initializing a database client from a URL.
+
 # v3.3.0
 
 - [fixed] Fixing a regression introduced in 3.2.0, where `VerifyIDToken()`

firebase.go

@@ -79,11 +79,18 @@ func (a *App) Auth(ctx context.Context) (*auth.Client, error) {
 	return auth.NewClient(ctx, conf)
 }
 
-// Database returns an instance of db.Client.
+// Database returns an instance of db.Client to interact with the default Firebase Database
+// configured via Config.DatabaseURL.
 func (a *App) Database(ctx context.Context) (*db.Client, error) {
+	return a.DatabaseWithURL(ctx, a.dbURL)
+}
+
+// DatabaseWithURL returns an instance of db.Client to interact with the Firebase Database
+// identified by the given URL.
+func (a *App) DatabaseWithURL(ctx context.Context, url string) (*db.Client, error) {
 	conf := &internal.DatabaseConfig{
 		AuthOverride: a.authOverride,
-		URL:          a.dbURL,
+		URL:          url,
 		Opts:         a.opts,
 		Version:      Version,
 	}

firebase_test.go

@@ -246,6 +246,10 @@ func TestDatabase(t *testing.T) {
 	if c, err := app.Database(ctx); c == nil || err != nil {
 		t.Errorf("Database() = (%v, %v); want (db, nil)", c, err)
 	}
+	url := "https://other-mock-db.firebaseio.com"
+	if c, err := app.DatabaseWithURL(ctx, url); c == nil || err != nil {
+		t.Errorf("Database() = (%v, %v); want (db, nil)", c, err)
+	}
 }
 
 func TestDatabaseAuthOverrides(t *testing.T) {