gnu: Add rust-tracing-0.1.

* gnu/packages/crates-io.scm (rust-tracing-0.1): New variable.

gnu/packages/crates-io.scm

@@ -28197,6 +28197,35 @@ server @code{Service} tests.")
 @code{Service}.")
     (license license:expat)))
 
+(define-public rust-tracing-0.1
+  (package
+    (name "rust-tracing")
+    (version "0.1.20")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (crate-uri "tracing" version))
+       (file-name (string-append name "-" version ".tar.gz"))
+       (sha256
+        (base32
+         "0hwgbyflibmsz7x6v7ndchnx1qvv43pg18419ji2y7pflzkmngbi"))))
+    (build-system cargo-build-system)
+    (arguments
+     `(#:cargo-inputs
+       (("rust-cfg-if" ,rust-cfg-if-0.1)
+        ("rust-log" ,rust-log-0.4)
+        ("rust-tracing-attributes" ,rust-tracing-attributes-0.1)
+        ("rust-tracing-core" ,rust-tracing-core-0.1))
+       #:cargo-development-inputs
+       (("rust-criterion" ,rust-criterion-0.3)
+        ("rust-futures" ,rust-futures-0.1)
+        ("rust-log" ,rust-log-0.4))))
+    (home-page "https://tokio.rs")
+    (synopsis "Application-level tracing for Rust")
+    (description "@code{rust-tracing} is a framework for instrumenting Rust
+programs to collect structured, event-based diagnostic information.")
+    (license license:expat)))
+
 
 (define-public rust-tracing-core-0.1
   (package