Use `defonce` instead of `def` for config.

src/taoensso/timbre.clj

@@ -21,7 +21,8 @@
   [& xs]
   (print (str (str/join \space xs) \newline)))
 
-(def config
+(defonce config
+  ^{:doc
     "This map atom controls everything about the way Timbre operates. In
     particular note the flexibility to add arbitrary appenders.
 
@@ -32,7 +33,7 @@
       :ap-config, :level, :error?, :instant, :timestamp, :ns, :message, :more,
       :profiling-stats (when applicable)
 
-  See source code for examples."
+    See source code for examples."}
   (atom {:current-level :debug
 
          ;;; Allow log filtering by namespace patterns (e.g. ["my-app.*"]).