A MongoDB adaptor for r2d2 connection pool.
```rust extern crate r2d2; extern crate r2d2_mongodb;
use r2d2::Pool; use r2d2_mongodb::{ConnectionOptionsBuilder, MongodbConnectionManager};
fn main () { let manager = MongodbConnectionManager::new( ConnectionOptionsBuilder::new() .withhost("localhost") .withport(27017) .withdb("admin") .withusername("root") .with_password("password") .build() );
let pool = Pool::builder()
.max_size(64)
.build(manager)
.unwrap();
//...
} ```