  Recently, Lee \textit{et. al.} [Nano Lett. \textbf{21}, 4305 (2021)] newly
synthesized monochalcogenide GeSe in a polar phase, referred to as
$\gamma$-phase. Motivated by this work, we study shift current of $\gamma$-GeSe
and its tunability via an in-plane uniaxial strain. Using first-principles
calculations, we uncover the electronic structure of the strained $\gamma$-GeSe
systems. We then calculate frequency-dependent shift current conductivities at
various strains. The tunability is demonstrated to enhance the shift current up
to $\sim$ 20 $\mu$A/V$^2$. Moreover, the direction of shift current can be
inverted by a light strain. Markedly, an anomalous behavior is found in the
zero-frequency limit, which can be an indicative of band inversion and a
potential topological phase transition driven by the strain. Our results
suggest that shift current can be a tangible prove of bulk electronic states of
$\gamma$-GeSe.
