How to make pool as static variable?

[TheGP]

I cant even return pool connection from a function

use diesel_async::pooled_connection::AsyncDieselConnectionManager;
use diesel_async::pooled_connection::deadpool::Pool;
use diesel_async::RunQueryDsl;
use diesel_async::AsyncPgConnection;

fn create_db_pool() -> Pool<AsyncDieselConnectionManager<AsyncPgConnection>> {
    dotenv().ok();

	let config = AsyncDieselConnectionManager::<diesel_async::AsyncPgConnection>::new(std::env::var("DATABASE_URL")?);
	let pool = Pool::builder(config)
		.max_size(20)
		.build()?;
	
	pool
}

But got

error[E0277]: the trait bound `AsyncDieselConnectionManager<AsyncPgConnection>: PoolableConnection` is not satisfied
   --> lib/src/lib.rs:22:24
    |
22  | fn create_db_pool() -> Pool<AsyncDieselConnectionManager<AsyncPgConnection>> {
    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `PoolableConnection` is not implemented for `AsyncDieselConnectionManager<AsyncPgConnection>`, which is required by `AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>: deadpool::managed::Manager`
    |
    = help: the trait `PoolableConnection` is implemented for `AsyncPgConnection`
    = note: required for `AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>` to implement `deadpool::managed::Manager`
note: required by a bound in `deadpool::managed::Pool`
   --> /home/eugenebos/.cargo/registry/src/index.crates.io-6f17d22bba15001f/deadpool-0.12.1/src/managed/mod.rs:249:20
    |
249 | pub struct Pool<M: Manager, W: From<Object<M>> = Object<M>> {
    |                    ^^^^^^^ required by this bound in `Pool`

error[E0277]: the trait bound `AsyncDieselConnectionManager<AsyncPgConnection>: DerefMut` is not satisfied
   --> lib/src/lib.rs:22:24
    |
22  | fn create_db_pool() -> Pool<AsyncDieselConnectionManager<AsyncPgConnection>> {
    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `DerefMut` is not implemented for `AsyncDieselConnectionManager<AsyncPgConnection>`, which is required by `AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>: deadpool::managed::Manager`
    |
    = help: the trait `deadpool::managed::Manager` is implemented for `AsyncDieselConnectionManager<C>`
    = note: required for `AsyncDieselConnectionManager<AsyncPgConnection>` to implement `AsyncConnection`
    = note: required for `AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>` to implement `deadpool::managed::Manager`
note: required by a bound in `deadpool::managed::Pool`
   --> /home/eugenebos/.cargo/registry/src/index.crates.io-6f17d22bba15001f/deadpool-0.12.1/src/managed/mod.rs:249:20
    |
249 | pub struct Pool<M: Manager, W: From<Object<M>> = Object<M>> {
    |                    ^^^^^^^ required by this bound in `Pool`

error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
  --> lib/src/lib.rs:31:113
   |
22 | fn create_db_pool() -> Pool<AsyncDieselConnectionManager<AsyncPgConnection>> {
   | ---------------------------------------------------------------------------- this function should return `Result` or `Option` to accept `?`
...
31 |     let config = AsyncDieselConnectionManager::<diesel_async::AsyncPgConnection>::new(std::env::var("DATABASE_URL")?);
   |                                                                                                                    ^ cannot use the `?` operator in a function that returns `deadpool::managed::Pool<AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>>`
   |
   = help: the trait `FromResidual<Result<Infallible, VarError>>` is not implemented for `deadpool::managed::Pool<AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>>`

error[E0277]: the trait bound `AsyncDieselConnectionManager<AsyncPgConnection>: PoolableConnection` is not satisfied
   --> lib/src/lib.rs:31:84
    |
31  |     let config = AsyncDieselConnectionManager::<diesel_async::AsyncPgConnection>::new(std::env::var("DATABASE_URL")?);
    |                                                                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `PoolableConnection` is not implemented for `AsyncDieselConnectionManager<AsyncPgConnection>`, which is required by `AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>: deadpool::managed::Manager`
    |
    = help: the trait `PoolableConnection` is implemented for `AsyncPgConnection`
    = note: required for `AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>` to implement `deadpool::managed::Manager`
note: required by a bound in `deadpool::managed::Pool`
   --> /home/eugenebos/.cargo/registry/src/index.crates.io-6f17d22bba15001f/deadpool-0.12.1/src/managed/mod.rs:249:20
    |
249 | pub struct Pool<M: Manager, W: From<Object<M>> = Object<M>> {
    |                    ^^^^^^^ required by this bound in `Pool`

error[E0277]: the trait bound `AsyncDieselConnectionManager<AsyncPgConnection>: DerefMut` is not satisfied
   --> lib/src/lib.rs:31:84
    |
31  |     let config = AsyncDieselConnectionManager::<diesel_async::AsyncPgConnection>::new(std::env::var("DATABASE_URL")?);
    |                                                                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `DerefMut` is not implemented for `AsyncDieselConnectionManager<AsyncPgConnection>`, which is required by `AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>: deadpool::managed::Manager`
    |
    = help: the trait `deadpool::managed::Manager` is implemented for `AsyncDieselConnectionManager<C>`
    = note: required for `AsyncDieselConnectionManager<AsyncPgConnection>` to implement `AsyncConnection`
    = note: required for `AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>` to implement `deadpool::managed::Manager`
note: required by a bound in `deadpool::managed::Pool`
   --> /home/eugenebos/.cargo/registry/src/index.crates.io-6f17d22bba15001f/deadpool-0.12.1/src/managed/mod.rs:249:20
    |
249 | pub struct Pool<M: Manager, W: From<Object<M>> = Object<M>> {
    |                    ^^^^^^^ required by this bound in `Pool`

error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
  --> lib/src/lib.rs:34:11
   |
22 | fn create_db_pool() -> Pool<AsyncDieselConnectionManager<AsyncPgConnection>> {
   | ---------------------------------------------------------------------------- this function should return `Result` or `Option` to accept `?`
...
34 |         .build()?;
   |                 ^ cannot use the `?` operator in a function that returns `deadpool::managed::Pool<AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>>`
   |
   = help: the trait `FromResidual<Result<Infallible, deadpool::managed::builder::BuildError>>` is not implemented for `deadpool::managed::Pool<AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>>`

error[E0277]: the trait bound `AsyncDieselConnectionManager<AsyncPgConnection>: PoolableConnection` is not satisfied
   --> lib/src/lib.rs:32:13
    |
32  |       let pool = Pool::builder(config)
    |  ________________^
33  | |         .max_size(20)
34  | |         .build()?;
    | |_________________^ the trait `PoolableConnection` is not implemented for `AsyncDieselConnectionManager<AsyncPgConnection>`, which is required by `AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>: deadpool::managed::Manager`
    |
    = help: the trait `PoolableConnection` is implemented for `AsyncPgConnection`
    = note: required for `AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>` to implement `deadpool::managed::Manager`
note: required by a bound in `deadpool::managed::Pool`
   --> /home/eugenebos/.cargo/registry/src/index.crates.io-6f17d22bba15001f/deadpool-0.12.1/src/managed/mod.rs:249:20
    |
249 | pub struct Pool<M: Manager, W: From<Object<M>> = Object<M>> {
    |                    ^^^^^^^ required by this bound in `Pool`

error[E0308]: mismatched types
  --> lib/src/lib.rs:36:2
   |
22 | fn create_db_pool() -> Pool<AsyncDieselConnectionManager<AsyncPgConnection>> {
   |                        ----------------------------------------------------- expected `deadpool::managed::Pool<AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>>` because of return type
...
36 |     pool
   |     ^^^^ expected `AsyncDieselConnectionManager<AsyncPgConnection>`, found `AsyncPgConnection`
   |
   = note: expected struct `deadpool::managed::Pool<AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>, deadpool::managed::Object<AsyncDieselConnectionManager<AsyncDieselConnectionManager<AsyncPgConnection>>>>`
              found struct `deadpool::managed::Pool<AsyncDieselConnectionManager<AsyncPgConnection>, deadpool::managed::Object<AsyncDieselConnectionManager<AsyncPgConnection>>>`

warning: unused import: `std::error::Error`
 --> lib/src/structs.rs:2:5
  |
2 | use std::error::Error;
  |     ^^^^^^^^^^^^^^^^^