refactor: move postgres to pg package (#1781)

core/stores/postgres/postgresql.go

@@ -1,14 +1,7 @@
 package postgres
 
-import (
-	// imports the driver, don't remove this comment, golint requires.
-	_ "github.com/lib/pq"
-	"github.com/zeromicro/go-zero/core/stores/sqlx"
-)
+import "github.com/zeromicro/go-zero/core/stores/pg"
 
-const postgresDriverName = "postgres"
-
-// New returns a postgres connection.
-func New(datasource string, opts ...sqlx.SqlOption) sqlx.SqlConn {
-	return sqlx.NewSqlConn(postgresDriverName, datasource, opts...)
-}
+// New creates a new postgresql store.
+// Deprecated: use pg.New instead.
+var New = pg.New