Does a type assertion / type switch have bad performance / is slow in Go?

Question

How slow is using type assertions / type switches in Go, as a method of run-time type discovery?

I\'ve heard that in C/C++ for example, discovering types at run time

Answer 1

In your

switch v := anything.(type) {
    case SomeCustomType:
        fmt.Println(v)
...

if you need not SomeCustomType.Fields or methods like in fmt.Println(v), doing

switch anything.(type) { //avoid 'v:= ' interface conversion, only assertion
    case SomeCustomType:
        fmt.Println("anything type is SomeCustomType", anything)
...

should be approximately two times faster