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

I run bench example by @siritinga in my laptop (go1.7.3 linux/amd64), got this result:

$ go test -bench .
BenchmarkIntmethod-4            2000000000               1.99 ns/op
BenchmarkInterface-4            1000000000               2.30 ns/op
BenchmarkTypeSwitch-4           2000000000               1.80 ns/op
BenchmarkTypeAssertion-4        2000000000               1.67 ns/op