How to write left aligned multi-line conclusion in inference rule?

This question is very similar to How to write centered multi-line conclusion in inference rule?. However, I can't figure out how to align an multi-line conclusion on the left. What am I missing? I'm using the semantic package to write inference rules:

\documentclass{article}
\usepackage[inference]{semantic}
\usepackage{amsmath}

\begin{document}

\inference{expr}{ \begin{aligned} This is a very long \\ expression \end{aligned} }
\inference{expr}{ \begin{gathered} This is a very long \\ expression \end{gathered} }

\end{document}


In this code, The first conclusion is aligned on the right. The second one is aligned in the middle. How can I align it on the left? Using align or flalign doesn't work and yields the following error:

! Package amsmath Error: \begin{align} allowed only in paragraph mode.
! Package amsmath Error: \begin{flalign} allowed only in paragraph mode.


I finally solved it by using the array environment:
\documentclass{article}