He touches upon it in the "Runtime Overhead" section, but I think when calling Go from C like this you loose a lot of the goodness of Goroutines, and any code making heavy use of Goroutines could become seriously problematic.
In native Go, Goroutines are very lightweight and cooperatively scheduled. In a CGo env I believe they each have an OS thread and a full stack. Source: https://www.cockroachlabs.com/blog/the-cost-and-complexity-o...