Specify MSRV in Cargo.toml

Cargo.toml

@@ -10,6 +10,8 @@ license = "MIT OR Apache-2.0"
 repository = "https://github.com/bikeshedder/deadpool"
 readme = "README.md"
 
+rust-version = "1.54.0"
+
 [package.metadata.docs.rs]
 all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
@@ -23,7 +25,7 @@ rt_async-std_1 = ["deadpool-runtime/async-std_1"]
 
 [dependencies]
 num_cpus = "1.11.1"
-retain_mut ="0.1.6"
+retain_mut = "0.1.6"
 # `managed` feature
 async-trait = { version = "0.1.17", optional = true }
 # `serde` feature
@@ -40,7 +42,12 @@ async-std = { version = "1.0", features = ["attributes"] }
 config = { version = "0.13", features = ["json"] }
 criterion = { version = "0.3.4", features = ["html_reports", "async_tokio"] }
 itertools = "0.10.3"
-tokio = { version = "1.5.0", features = ["macros", "rt", "rt-multi-thread", "time"] }
+tokio = { version = "1.5.0", features = [
+    "macros",
+    "rt",
+    "rt-multi-thread",
+    "time",
+] }
 
 [[bench]]
 name = "managed"
@@ -62,5 +69,5 @@ members = [
     "runtime",
     "sqlite",
     "sync",
-    "examples/*"
+    "examples/*",
 ]