Passing Colour from program to vertex shader
I don't know what language that is, but I'm going to hazard a guess that the arrays points and gl.Ptr([]float32{0.5,0.5,0.0}) are not the same size. If you intend to provide per-vertex colors, then you must provide one color for every vertex. If you want to provide a single color that all vertices share, then that would be a uniform, not a vertex shader input.

Also, commenting out your layout declarations isn't helping. Though if you are going to declare a location for the VS output variable, then the matching FS input needs to have the same location declared.