Add new env vars (#1481)

(cherry picked from commit 643a055)

docs/sources/reference/cli/environment-variables.md

@@ -14,25 +14,35 @@ The following environment variables are supported:
 
 * `GODEBUG`
 * `HTTP_PROXY`
+* `PPROF_MUTEX_PROFILING_PERCENT`
+* `PPROF_BLOCK_PROFILING_RATE`
 
 Refer to the [Go runtime][runtime] documentation for more information about Go runtime environment variables.
 
-## Arguments
+## GODEBUG
 
-The following arguments are supported.
-
-### GODEBUG
+You can use the `GODEBUG` environment variable to control the debugging variables within the Go runtime.  The following arguments are supported.
 
 Argument                        | Description                                                                                          | Default
 --------------------------------|------------------------------------------------------------------------------------------------------|--------
 `x509usefallbackroots`          | Enforce a fallback on the X.509 trusted root certificates. Set to `1` to enable.                     | `0`
 `netdns`                        | Force a resolver. Set to `go` for a pure Go resolver. Set to `cgo` or `win32` for a native resolver. |
 `netdns`                        | Show resolver debugging information. Set to `1` for basic information. Set to `2` for verbose.       |
 
-### HTTP_PROXY
+## HTTP_PROXY
+
+You can use the `HTTP_PROXY` environment variable to define the hostname or IP address of the proxy server.  For example, you can set the proxy to `http://proxy.example.com`.
+
+## PPROF_MUTEX_PROFILING_PERCENT
+
+You can use the `PPROF_MUTEX_PROFILING_PERCENT` environment variable to define the percentage of mutex profiles to retrieve from the pprof mutex endpoint. If you set this variable to `5`, then 5 percent of the mutexes are sampled. The default value is `0.01`.
+
+## PPROF_BLOCK_PROFILING_RATE
+
+You can use the `PPROF_BLOCK_PROFILING_RATE` environment variable to define the rate that mutexes are tracked. You can use the following values with this environment variable. The default value is `10000`.
 
-Argument                   | Description                                     | Default
----------------------------|-------------------------------------------------|--------
-`http://proxy.example.com` | The hostname or IP address of the proxy server. |
+* `0`: Nothing is tracked.
+* `1`: All mutexes are tracked.
+* A value greater than `1`: The number of nanoseconds to track mutexes.
 
 [runtime]: https://pkg.go.dev/runtime