This is a Go matrix and vector math library specialized for Open GL graphics capabilities.
This package is made primarily with code generation for the basic vector and matrix operations, though and functionality beyond that is handwritten.
Vectors and matrices are stored in Column Major Order, just like OpenGL, which means the "transpose" argument should be false when passing in vectors and matrices using this package.
This package is split into two sub-packages. The package mgl32 deals with 32-bit floats, and mgl64 deals with 64-bit ones. Generally you'll use the 32-bit ones with OpenGL, but the 64-bit one is available in case you use the double extension or simply want to do higher precision 3D math without OpenGL.
The old repository, before the split between the 32-bit and 64-bit subpackages, is kept at github.com/Jragonmiris/mathgl (the old repository path), but is no longer maintained.
Examples can be found in github.com/go-gl/example.
You're probably using a combination of go get and an old Go version. The go get utility is programmed to look for tags matching the current Go version. Right now there's a tag for Go1.2.2 for instance, so if you haven't upgraded to Go1.3, go get will grab an older API. See the API Changes section for details on the version tagging.
Feel free to submit pull requests for features and bug fixes. Do note that, aside from documentation bugs, meta (travis.yml etc) fixes, example code, and extremely trivial changes (basic accessors) pull requests will not be accepted without tests corresponding to the new code. If it's a bug fix, the test should test the bug.
mgl64 is generated directly from 32-bit version. To reflect your changes run go generate github.com/go-gl/mathgl/mgl32 (or just go generate in mgl32 directory). Also note that since code generation is used in matrix.go and vector.go, no changes should be made to those files directly. Edit matrix.tmpl or vector.tmpl and run go generate.
From now on, no major API breaking changes will be made between Go version releases. That means any time any "x" in Go1.x.x increases. Exceptions are made, of course, for bug fixes. If a bug fix necessitates changing semantics of calling software, it will be changed. (An example is the recent update of Transpose which was mistakenly using row major rules). Deprecated functions may also be nuked at major version released. Before any API breaking changes near major releases, the most recent non-breaking commit will be tagged with the previous Go version number (e.g. Go1.2.2). If no such tag exists, one can assume nothing has been broken.
Removal of EulerToQuat; use AnglesToQuat with the order ZYX instead.