update README.md

README.md

@@ -2,6 +2,42 @@
 --
     import "github.com/go-i2p/logger"
 
+Originally written by @hkh4n, modified by @eyedeekay.
+
+Package logger provides a logger for go-i2p.
+It is basically a wrapper around logrus that implements "fast-fail" behavior when an environment variable is set.
+Right now it only wraps the parts of logrus that we use but if we need more, we can add them.
+
+## Verbosity ##
+Logging can be enabled and configured using the `DEBUG_I2P` environment variable. By default, logging is disabled.
+
+There are three available log levels:
+
+- Debug
+```shell
+export DEBUG_I2P=debug
+```
+- Warn
+```shell
+export DEBUG_I2P=warn
+```
+- Error
+```shell
+export DEBUG_I2P=error
+```
+
+If DEBUG_I2P is set to an unrecognized variable, it will fall back to "debug".
+
+## Fast-Fail mode ##
+
+Fast-Fail mode can be activated by setting `WARNFAIL_I2P` to any non-empty value. When set, every warning or error is Fatal.
+It is unsafe for production use, and intended only for debugging and testing purposes.
+
+```shell
+export WARNFAIL_I2P=true
+```
+
+If `WARNFAIL_I2P` is set and `DEBUG_I2P` is unset, `DEBUG_I2P` will be set to `debug`.
 
 ## Usage