diff --git a/Cargo.toml b/Cargo.toml
index 7c9a897..4c82032 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,11 +6,11 @@ edition = "2018"
 build = "src/build.rs"
 
 [dependencies]
-users = "0.11.0"
+users = "0.10.0"
 regex = "1.0.1"
 futures = "0.3"
 async-trait = "0.1"
-tokio = { version = "0.3", features = ["rt", "process", "io-util", "macros", "sync"] }
+tokio = { version = "0.2", features = ["process", "io-util", "rt-core", "macros", "sync"] }
 once_cell = "1.4"
 
 [dev-dependencies]
diff --git a/src/async_utils.rs b/src/async_utils.rs
index c656c53..2c1196a 100644
--- a/src/async_utils.rs
+++ b/src/async_utils.rs
@@ -6,15 +6,11 @@ use std::{
   thread,
   time::Duration,
 };
-use tokio::runtime::Builder;
 
 pub use async_trait::async_trait;
 
 pub fn run<F: Future>(future: F) -> F::Output {
-  Builder::new_current_thread()
-    .build()
-    .unwrap()
-    .block_on(future)
+  tokio::runtime::Runtime::new().unwrap().block_on(future)
 }
 pub use tokio::try_join;
 
diff --git a/src/builder.rs b/src/builder.rs
index 811c3f1..481096d 100644
--- a/src/builder.rs
+++ b/src/builder.rs
@@ -719,7 +719,9 @@ impl<D: Clone> ImplementationBuilder<MariaDbDatabase<D>> for DefaultBuilder {
 
 impl<D: Clone> ImplementationBuilder<PostgresqlDatabase<D>> for DefaultBuilder {
   type Prerequisites = ();
-  fn prerequisites(_: &PostgresqlDatabase<D>) -> Self::Prerequisites {}
+  fn prerequisites(_: &PostgresqlDatabase<D>) -> Self::Prerequisites {
+    ()
+  }
 
   type Implementation = (PostgreSQLDatabaseSymbol<'static, String, String, StdCommandRunner>,);
   fn create(
diff --git a/src/command_runner.rs b/src/command_runner.rs
index 0a64621..b69e7ee 100644
--- a/src/command_runner.rs
+++ b/src/command_runner.rs
@@ -72,7 +72,6 @@ impl CommandRunner for StdCommandRunner {
       .expect("Failed to write to stdin");
     let res = child.wait_with_output().await;
     //println!("{:?}", res);
-    #[allow(clippy::let_and_return)]
     res
   }
 }
diff --git a/src/loggers.rs b/src/loggers.rs
index dcbd0e1..e5c8573 100644
--- a/src/loggers.rs
+++ b/src/loggers.rs
@@ -80,7 +80,7 @@ pub struct FilteringLogger<'a, L> {
 }
 
 impl<'a, L> FilteringLogger<'a, L> {
-  pub const fn new(logger: &'a L, max_level: Level) -> Self {
+  pub fn new(logger: &'a L, max_level: Level) -> Self {
     Self { logger, max_level }
   }
 }
@@ -104,7 +104,6 @@ pub struct StoringLogger {
 }
 
 impl StoringLogger {
-  #[must_use]
   pub fn new() -> Self {
     Self::default()
   }
diff --git a/src/setup/mod.rs b/src/setup/mod.rs
index a187a88..cca4db8 100644
--- a/src/setup/mod.rs
+++ b/src/setup/mod.rs
@@ -7,6 +7,5 @@ pub use symbol_runner::{
   SymbolRunner,
 };
 mod runnable;
-#[allow(clippy::module_inception)]
 mod setup;
 pub use setup::SetupFacade as Setup;
diff --git a/src/setup/runnable.rs b/src/setup/runnable.rs
index 4e3e087..add3f49 100644
--- a/src/setup/runnable.rs
+++ b/src/setup/runnable.rs
@@ -16,7 +16,6 @@ pub trait Runnable {
 }
 
 #[async_trait(?Send)]
-#[allow(clippy::use_self)]
 impl<S> Runnable for S
 where
   Self: Symbol + Debug,
diff --git a/src/setup/setup.rs b/src/setup/setup.rs
index 472d52e..842152b 100644
--- a/src/setup/setup.rs
+++ b/src/setup/setup.rs
@@ -242,9 +242,7 @@ mod test {
     fn from_artifact(_from: ()) -> Self {
       Self
     }
-    #[allow(clippy::unused_unit)]
     fn into_artifact(self) -> () {
-      #[allow(clippy::unused_unit)]
       ()
     }
   }
diff --git a/src/storage.rs b/src/storage.rs
index aa4ce9d..a963414 100644
--- a/src/storage.rs
+++ b/src/storage.rs
@@ -14,7 +14,6 @@ pub trait Storage {
 pub struct SimpleStorage(PathBuf);
 
 impl SimpleStorage {
-  #[must_use]
   pub const fn new(base: PathBuf) -> Self {
     Self(base)
   }
diff --git a/src/symbols/dir.rs b/src/symbols/dir.rs
index 1a60af2..f9fdacc 100644
--- a/src/symbols/dir.rs
+++ b/src/symbols/dir.rs
@@ -11,7 +11,7 @@ pub struct Dir<P> {
 }
 
 impl<P> Dir<P> {
-  pub const fn new(path: P) -> Self {
+  pub fn new(path: P) -> Self {
     Self { path }
   }
 }
diff --git a/src/symbols/file.rs b/src/symbols/file.rs
index a3763c1..edff275 100644
--- a/src/symbols/file.rs
+++ b/src/symbols/file.rs
@@ -12,7 +12,7 @@ pub struct File<D, C> {
 }
 
 impl<D, C> File<D, C> {
-  pub const fn new(path: D, content: C) -> Self {
+  pub fn new(path: D, content: C) -> Self {
     Self { path, content }
   }
 }
diff --git a/src/symbols/git/submodules.rs b/src/symbols/git/submodules.rs
index 5413b8d..e35eabf 100644
--- a/src/symbols/git/submodules.rs
+++ b/src/symbols/git/submodules.rs
@@ -13,7 +13,7 @@ pub struct GitSubmodules<'a, P, C> {
 }
 
 impl<'a, P, C> GitSubmodules<'a, P, C> {
-  pub const fn new(target: P, command_runner: &'a C) -> Self {
+  pub fn new(target: P, command_runner: &'a C) -> Self {
     Self {
       target,
       command_runner,
diff --git a/src/symbols/mariadb/dump.rs b/src/symbols/mariadb/dump.rs
index 1b503fa..8276532 100644
--- a/src/symbols/mariadb/dump.rs
+++ b/src/symbols/mariadb/dump.rs
@@ -34,8 +34,8 @@ impl<'a, N, C: CommandRunner, S> Dump<'a, N, C, S> {
 impl<N: AsRef<str>, C: CommandRunner, S: Storage> Symbol for Dump<'_, N, C, S> {
   async fn target_reached(&self) -> Result<bool, Box<dyn Error>> {
     let dump_date = self.storage.recent_date()?;
-    let output = self.run_sql(&format!("select UNIX_TIMESTAMP(MAX(UPDATE_TIME)) from information_schema.tables WHERE table_schema = '{}'", self.db_name.as_ref())).await?;
-    let modified_date = output.trim_end();
+    let _modified_date = self.run_sql(&format!("select UNIX_TIMESTAMP(MAX(UPDATE_TIME)) from information_schema.tables WHERE table_schema = '{}'", self.db_name.as_ref())).await?;
+    let modified_date = _modified_date.trim_end();
     Ok(modified_date != "NULL" && u64::from_str(modified_date)? <= dump_date)
   }
 
diff --git a/src/symbols/systemd/user_session.rs b/src/symbols/systemd/user_session.rs
index 1f41d46..5de3342 100644
--- a/src/symbols/systemd/user_session.rs
+++ b/src/symbols/systemd/user_session.rs
@@ -11,7 +11,7 @@ pub struct UserSession<'a, U, C> {
 }
 
 impl<'a, U, C> UserSession<'a, U, C> {
-  pub const fn new(user_name: U, command_runner: &'a C) -> Self {
+  pub fn new(user_name: U, command_runner: &'a C) -> Self {
     Self {
       user_name,
       command_runner,
diff --git a/src/symbols/tls/csr.rs b/src/symbols/tls/csr.rs
index 4af3683..3b35681 100644
--- a/src/symbols/tls/csr.rs
+++ b/src/symbols/tls/csr.rs
@@ -14,7 +14,7 @@ pub struct Csr<C, D, K, P> {
 }
 
 impl<C, D, K, P> Csr<C, D, K, P> {
-  pub const fn new(command_runner: C, domain: D, key_path: K, csr_path: P) -> Self {
+  pub fn new(command_runner: C, domain: D, key_path: K, csr_path: P) -> Self {
     Self {
       command_runner,
       domain,
diff --git a/src/symbols/tls/key.rs b/src/symbols/tls/key.rs
index 720d7ab..c5287c0 100644
--- a/src/symbols/tls/key.rs
+++ b/src/symbols/tls/key.rs
@@ -8,17 +8,19 @@ use std::path::Path;
 pub struct Key<C, P> {
   file_path: P,
   command_runner: C,
-  bytes: u32,
 }
 
 impl<C, P> Key<C, P> {
-  pub const fn new(command_runner: C, file_path: P) -> Self {
+  pub fn new(command_runner: C, file_path: P) -> Self {
     Self {
       file_path,
       command_runner,
-      bytes: 4096,
     }
   }
+
+  fn get_bytes(&self) -> u32 {
+    4096
+  }
 }
 
 #[async_trait(?Send)]
@@ -55,7 +57,7 @@ impl<C: CommandRunner, P: AsRef<Path>> Symbol for Key<C, P> {
           "genrsa",
           "-out",
           self.file_path.as_ref(),
-          self.bytes.to_string(),
+          self.get_bytes().to_string(),
         ],
       )
       .await
diff --git a/src/symbols/user.rs b/src/symbols/user.rs
index db784a7..3c67809 100644
--- a/src/symbols/user.rs
+++ b/src/symbols/user.rs
@@ -15,7 +15,7 @@ pub struct User<U, C> {
 }
 
 impl<U, C> User<U, C> {
-  pub const fn new(user_name: U, command_runner: C) -> Self {
+  pub fn new(user_name: U, command_runner: C) -> Self {
     Self {
       user_name,
       command_runner,
diff --git a/src/templates/nginx/server.rs b/src/templates/nginx/server.rs
index 9f04bbd..fe7aa60 100644
--- a/src/templates/nginx/server.rs
+++ b/src/templates/nginx/server.rs
@@ -1,7 +1,6 @@
 use std::fmt::Display;
 use std::path::Path;
 
-#[must_use]
 pub fn default_server<P: AsRef<Path>>(challenges_snippet_path: P) -> String {
   format!(
     "server {{
@@ -13,7 +12,6 @@ pub fn default_server<P: AsRef<Path>>(challenges_snippet_path: P) -> String {
   )
 }
 
-#[must_use]
 pub fn server_config<D: Display, C: AsRef<Path>, K: AsRef<Path>, T: Display, S: AsRef<Path>>(
   domain: D,
   cert_path: C,
@@ -55,7 +53,6 @@ server {{
   )
 }
 
-#[must_use]
 pub fn php_snippet<SOCKET: AsRef<Path>, STATIC: AsRef<Path>>(
   index: &'static str,
   socket_path: SOCKET,
@@ -74,7 +71,6 @@ pub fn php_snippet<SOCKET: AsRef<Path>, STATIC: AsRef<Path>>(
   )
 }
 
-#[must_use]
 pub fn redir_snippet(target: &str) -> String {
   format!(
     "location / {{
@@ -89,7 +85,6 @@ pub trait SocketSpec {
 }
 
 impl<T: AsRef<Path>> SocketSpec for T {
-  #[must_use]
   fn to_nginx(&self) -> String {
     format!("unix:{}:", self.as_ref().to_str().unwrap())
   }
@@ -99,20 +94,17 @@ impl<T: AsRef<Path>> SocketSpec for T {
 pub struct LocalTcpSocket(usize);
 
 impl LocalTcpSocket {
-  #[must_use]
   pub const fn new(x: usize) -> Self {
     Self(x)
   }
 }
 
 impl SocketSpec for LocalTcpSocket {
-  #[must_use]
   fn to_nginx(&self) -> String {
     format!("localhost:{}", self.0)
   }
 }
 
-#[must_use]
 pub fn proxy_snippet<S: SocketSpec, STATIC: AsRef<Path>>(
   socket_path: &S,
   static_path: STATIC,
@@ -133,7 +125,6 @@ pub fn proxy_snippet<S: SocketSpec, STATIC: AsRef<Path>>(
   )
 }
 
-#[must_use]
 pub fn static_snippet<S: AsRef<Path>>(static_path: S) -> String {
   format!(
     "root                    {};
@@ -143,7 +134,6 @@ pub fn static_snippet<S: AsRef<Path>>(static_path: S) -> String {
   )
 }
 
-#[must_use]
 pub fn dokuwiki_snippet() -> String {
   "
   location ~ /(data/|conf/|bin/|inc/|install.php) { deny all; }
@@ -159,7 +149,6 @@ pub fn dokuwiki_snippet() -> String {
   }".into()
 }
 
-#[must_use]
 pub fn nextcloud_snippet() -> String {
   "
   client_max_body_size 500M;