It's a very small performance hit because it doesn't do the work to be uniformly random, just "not always the same". If you think about how you have to iterate

It's a very small performance hit because it doesn't do the work to be uniformly random, just "not always the same". If you think about how you have to iterate through a hash table or similar data structure anyhow, it's either O(1) or O(log n) paid once per "range" on the data structure, which is dwarfed by the actual act of ranging on the data structure. Go's philosophy is also definitely willing to pay that price to avoid a large class of known bugs that has hit all kinds of code bases. It is not about being the fastest language. As compiled languages go, it's solidly middle-tier, and not likely to go up much from there. (Among the C-style compiled languages, it's low-tier on performance, at around half the speed of C in general. However there's enough compiled languages like Haskell that are still generally relatively slow so that Go is mid-tier for compiled languages over all.)