message: Fix up benchmark
diff: @@ -7,7 +7,7 @@ use tokio::runtime::Runtime;
  use tokio_postgres::{Client, NoTls};
  fn setup() -> (Client, Runtime) {
  - let runtime = Runtime::new().unwrap();
  + let mut runtime = Runtime::new().unwrap();
  let (client, conn) = runtime
  .block_on(tokio_postgres::connect(
  "host=localhost port=5433 user=postgres",
  @@ -19,7 +19,7 @@ fn setup() -> (Client, Runtime) {
  }
  fn query_prepared(c: &mut Criterion) {
  - let (client, runtime) = setup();
  + let (client, mut runtime) = setup();
  let statement = runtime.block_on(client.prepare("SELECT $1::INT8")).unwrap();
  c.bench_function("runtime_block_on", move |b| {
  b.iter(|| {
  @@ -29,13 +29,13 @@ fn query_prepared(c: &mut Criterion) {
  })
  });
  - let (client, runtime) = setup();
  + let (client, mut runtime) = setup();
  let statement = runtime.block_on(client.prepare("SELECT $1::INT8")).unwrap();
  c.bench_function("executor_block_on", move |b| {
  b.iter(|| executor::block_on(client.query(&statement, &[&1i64])).unwrap())
  });
  - let (client, runtime) = setup();
  + let (client, mut runtime) = setup();
  let client = Arc::new(client);
  let statement = runtime.block_on(client.prepare("SELECT $1::INT8")).unwrap();
  c.bench_function("spawned", move |b| {
  