interface{} is nothing like void* because it's type-safe. interface{} is (type, value) i.e. it remembers the type of the value it contains.
void * is just a value.
In C a cast is unsafe because it doesn't tell you if you did something wrong.
In Go, type assertion is safe. It tells you if it succeeded and if you ignore it, it'll panic, informing you that you have tried to perform an illegal operation.
interface{} is nothing like void* because it's type-safe. interface{} is (type, value) i.e. it remembers the type of the value it contains. void * is just a value.
Your code snippet has a bug because you didn't check the type assertion result. Here's a fixed version: http://play.golang.org/p/vlsXtEmgMs
In C a cast is unsafe because it doesn't tell you if you did something wrong.
In Go, type assertion is safe. It tells you if it succeeded and if you ignore it, it'll panic, informing you that you have tried to perform an illegal operation.
For more see: http://golang.org/ref/spec#Type_assertions