import std.digest.sha : SHA1;
import std.string : representation;
auto hmac = HMAC!SHA1("My s3cR3T keY".representation);
hmac.put("Hello, world".representation);
static immutable expected = [
    130, 32, 235, 44, 208, 141,
    150, 232, 211, 214, 162, 195,
    188, 127, 52, 89, 100, 68, 90, 216];
assert(hmac.finish() == expected);