message: Crate level docs
diff: +//! A synchronous client for the PostgreSQL database.
  //!
  +//! # Example
  +//!
  +//! ```no_run
  +//! use postgres::{Client, NoTls};
  +//!
  +//! # fn main() -> Result<(), postgres::Error> {
  +//! let mut client = Client::connect("host=localhost user=postgres", NoTls)?;
  +//!
  +//! client.simple_query("
  +//! CREATE TABLE person (
  +//! id SERIAL PRIMARY KEY,
  +//! name TEXT NOT NULL,
  +//! data BYTEA
  +//! )
  +//! ")?;
  +//!
  +//! let name = "Ferris";
  +//! let data = None::<&[u8]>;
  +//! client.execute(
  +//! "INSERT INTO person (name, data) VALUES ($1, $2)",
  +//! &[&name, &data],
  +//! )?;
  +//!
  +//! for row in client.query("SELECT id, name, data FROM person", &[])? {
  +//! let id: i32 = row.get(0);
  +//! let name: &str = row.get(1);
  +//! let data: Option<&[u8]> = row.get(2);
  +//!
  +//! println!("found person: {} {} {:?}", id, name, data);
  +//! }
  +//! # Ok(())
  +//! # }
  +//! ```
  +//!
  +//! # Implementation
  +//!
  +//! This crate is a lightweight wrapper over tokio-postgres. The `tokio_postgres::Connection` is spawned onto an
  +//! executor, and the `tokio_postgres::Client` is wrapped in the `postgres::Client`, which simply waits on the futures
  +//! the nonblocking client creates.
  +//!
  +//! # Runtime
  +//!
  +//! A client can be constructed directly from a `tokio-postgres` client via a `From` implementation, but the `runtime`
  +//! Cargo feature (enabled by default) provides a more convenient interface. By default, connections will be spawned
  +//! onto a static tokio `Runtime`, but a custom `Executor` can also be used instead.
  +//!
  +//! # SSL/TLS support
  +//!
  +//! TLS support is implemented via external libraries. `Client::connect` and `Config::connect` take a TLS implementation
  +//! as an argument. The `NoTls` type in this crate can be used when TLS is not required. Otherwise, the
  +//! `tokio-postgres-openssl` and `tokio-postgres-native-tls` crates provide implementations backed by the `postgres` and
  +//! `native-tls` crates, respectively.
  #![warn(clippy::all, rust_2018_idioms, missing_docs)]
  #[cfg(feature = "runtime")]
  