How to assert ast.TypeSpec to int type in Golang?

I have following code for Golang docs parsing. "ts" is ast.TypeSpec. I can check StructType and etc. But, ts.Type is "int". How can I assert for int and other basic type?

ts, ok := d.Decl.(*ast.TypeSpec)
switch ts.Type.(type) {
case *ast.StructType:
    fmt.Println("StructType")
case *ast.ArrayType:
    fmt.Println("ArrayType")
case *ast.InterfaceType:
    fmt.Println("InterfaceType")
case *ast.MapType:
    fmt.Println("MapType")
}