func identityMat4() [16]float { return { 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1 } }
I hope you get the idea
func identityMat4() [16]float64 { return [...]float64{ 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1 } }
(Click to play)