sharedLog = new FileLogger(yourFile);
The example sets a new FileLogger as new sharedLog.
If at some point you want to use the original default logger again, you can use sharedLog = null;. This will put back the original.
Note: While getting and setting sharedLog is thread-safe, it has to be considered that the returned reference is only a current snapshot and in the following code, you must make sure no other thread reassigns to it between reading and writing sharedLog.
sharedLog is only thread-safe if the used Logger is thread-safe. The default Logger is thread-safe.
if (sharedLog !is myLogger) sharedLog = new myLogger;
This property sets and gets the default Logger. Unless set to another logger by the user, the default logger's log level is LogLevel.info.