avoid messing with finalize cycle in Disposable.

ensure statements are closed when connection is closed

spec/result_set_spec.cr

@@ -1,5 +1,8 @@
 require "./spec_helper"
 
+class DummyException < Exception
+end
+
 describe DB::ResultSet do
   it "should enumerate records using each" do
     nums = [] of Int32
@@ -15,4 +18,28 @@ describe DB::ResultSet do
 
     nums.should eq([3, 4, 1, 2])
   end
+
+  it "should close ResultSet after query" do
+    with_dummy do |db|
+      the_rs = uninitialized DB::ResultSet
+      db.query "3,4 1,2" do |rs|
+        the_rs = rs
+      end
+      the_rs.closed?.should be_true
+    end
+  end
+
+  it "should close ResultSet after query even with exception" do
+    with_dummy do |db|
+      the_rs = uninitialized DB::ResultSet
+      begin
+        db.query "3,4 1,2" do |rs|
+          the_rs = rs
+          raise DummyException.new
+        end
+      rescue DummyException
+      end
+      the_rs.closed?.should be_true
+    end
+  end
 end