Fix flickering test

Author: jackc

pgconn/pgconn_test.go

@@ -2200,12 +2200,11 @@ func TestConnCopyFromConnectionTerminated(t *testing.T) {
 
 	closerConn, err := pgconn.Connect(ctx, os.Getenv("PGX_TEST_DATABASE"))
 	require.NoError(t, err)
+	defer closeConn(t, closerConn)
+	errChan := make(chan error, 1)
 	time.AfterFunc(500*time.Millisecond, func() {
-		// defer inside of AfterFunc instead of outer test function because outer function can finish while Read is still in
-		// progress which could cause closerConn to be closed too soon.
-		defer closeConn(t, closerConn)
 		err := closerConn.ExecParams(ctx, "select pg_terminate_backend($1)", [][]byte{[]byte(fmt.Sprintf("%d", pgConn.PID()))}, nil, nil, nil).Read().Err
-		require.NoError(t, err)
+		errChan <- err
 	})
 
 	_, err = pgConn.Exec(ctx, `create temporary table foo(
@@ -2238,6 +2237,9 @@ func TestConnCopyFromConnectionTerminated(t *testing.T) {
 	case <-time.After(5 * time.Second):
 		t.Fatal("Connection cleanup exceeded maximum time")
 	}
+
+	err = <-errChan
+	require.NoError(t, err)
 }
 
 func TestConnCopyFromGzipReader(t *testing.T) {