  The Goos-H{\"a}nchen (GH) shift is a specifical optical phenomenon that
describes a shift parallel to the reflected light inside the plane of
incidence, when a finite-width light undergoes total internal reflection at the
interface of medium. Although the GH shift in optics has been widely observed
experimentally, its generalization remains uncovered completely in relativistic
quantum mechanics for the existence of Klein's paradox. Recently, Wang has
solved Klein's paradox based on the different solutions adpoted for Dirac's
equation with step potential in corresponding energy regions
\href{https://dx.doi.org/10.1088/2399-6528/abd340}{[J. Phys. Commun. {\bf 4},
125010 (2020)]}. In the light of Wang's method, we calculate the GH shift for
Dirac fermions under relativistic conditions when they are incident obliquely
on a three-dimensional infinite potential barrier. Furthermore, we find that
the relativistic quantum GH shift can be negative, which is different from the
non-relativistic case.
