name                        old time/op    new time/op    delta
deco/unzlib/py/null-1K        2.12µs ± 1%    2.11µs ± 2%     ~     (p=0.841 n=5+5)
deco/unzlib/go/null-1K        1.89µs ± 1%    2.27µs ± 1%  +20.03%  (p=0.008 n=5+5)
deco/unzlib/py/null-4K        13.5µs ± 4%    13.3µs ± 0%     ~     (p=0.310 n=5+5)
deco/unzlib/go/null-4K        8.54µs ± 0%    8.91µs ± 0%   +4.43%  (p=0.008 n=5+5)
deco/unzlib/py/null-2M        5.20ms ±10%    5.31ms ± 1%     ~     (p=0.548 n=5+5)
deco/unzlib/go/null-2M        2.58ms ± 1%    3.87ms ± 0%  +50.13%  (p=0.008 n=5+5)
deco/unzlib/py/wczdata-avg    24.1µs ± 1%    23.9µs ± 0%     ~     (p=0.114 n=4+4)
deco/unzlib/go/wczdata-avg    68.0µs ± 1%    20.9µs ± 0%  -69.29%  (p=0.008 n=5+5)
deco/unzlib/py/wczdata-max    23.5µs ± 1%    23.5µs ± 0%     ~     (p=0.556 n=4+5)
deco/unzlib/go/wczdata-max    67.8µs ± 0%    20.7µs ± 1%  -69.45%  (p=0.008 n=5+5)
deco/unzlib/py/prod1-avg      4.47µs ± 2%    4.44µs ± 1%     ~     (p=0.341 n=5+5)
deco/unzlib/go/prod1-avg      11.0µs ± 0%     4.1µs ± 1%  -62.39%  (p=0.016 n=5+4)
deco/unzlib/py/prod1-max       326µs ± 0%     325µs ± 0%     ~     (p=0.095 n=5+5)
deco/unzlib/go/prod1-max       542µs ± 0%     262µs ± 0%  -51.71%  (p=0.008 n=5+5)

There is also unsafe interface with czlib.UnsafeDecompress & friends which I
had not tried because even using safe interface brings ~ 3x speedup.