Go port of Zopfli, a zlib-compatible compression library.
Zopfli compresses data more effectively than zlib does, at the expense of compression speed. The go-zopfli port is 2-3 times slower than the C version, and compresses at approximately 100 kB/s.
It can be used to compress files that will not change often or if you need a lower-level interface to Deflate compression.