Package expvar provides a standardized interface to public variables, such as operation counters in servers. It exposes these variables via HTTP at /debug/vars in JSON format.

Operations to set or modify these public variables are atomic.

In addition to adding the HTTP handler, this package registers the following variables:

cmdline   os.Args
memstats  runtime.Memstats

The package is sometimes only imported for the side effect of registering its HTTP handler and the above variables. To use it this way, link this package into your program:

import _ "expvar"