  The collection of high-quality photometric data by space telescopes is
revolutionizing the area of white-dwarf asteroseismology. Among the different
kinds of pulsating white dwarfs, there are those that have He-rich atmospheres,
and they are called DBVs or V777 Her variable stars. The archetype of these
pulsating white dwarfs, GD~358, is the focus of the present paper. We report a
thorough asteroseismological analysis of the DBV star GD~358 (TIC~219074038)
based on new high-precision photometric data gathered by the {\it TESS} space
mission combined with data taken from the Earth. In total, we detected 26
periodicities from the {\it TESS} light curve of this DBV star using a standard
pre-whitening. The oscillation frequencies are associated with nonradial
$g$(gravity)-mode pulsations with periods from $\sim 422$ s to $\sim 1087$ s.
Moreover, we detected 8 combination frequencies between $\sim 543$ s and $\sim
295$ s. We combined these data with a huge amount of observations from the
ground. We found a constant period spacing of $39.25\pm0.17$ s, which helped us
to infer its mass ($M_{\star}= 0.588\pm0.024 M_{\sun}$) and constrain the
harmonic degree $\ell$ of the modes. We carried out a period-fit analysis on
GD~358, and we were successful in finding an asteroseismological model with a
stellar mass ($M_{\star}= 0.584^{+0.025}_{-0.019} M_{\sun}$), in line with the
spectroscopic mass ($M_{\star}= 0.560\pm0.028 M_{\sun}$). We found that the
frequency splittings vary according to the radial order of the modes,
suggesting differential rotation. Obtaining a seismological made it possible to
estimate the seismological distance ($d_{\rm seis}= 42.85\pm 0.73$ pc) of
GD~358, which is in very good accordance with the precise astrometric distance
measured by {\it GAIA} EDR3 ($\pi= 23.244\pm 0.024, d_{\rm GAIA}= 43.02\pm
0.04$~pc).
