Add documentation for logger

logger/init.go

@@ -1,5 +1,14 @@
+// Package logger has implementation of loggers for mtglib.Logger
+// interface.
+//
+// Please see a description of that interface to get some agreements
+// which are used by mtglib.
 package logger
 
+// StdLikeLogger is an interface which is close to log.Logger. This is
+// commonly used by many 3pp tools. While mtglib itself does not need
+// it, it is always a good idea to support it and have a transient end
+// to end logging.
 type StdLikeLogger interface {
 	Printf(format string, args ...interface{})
 }

logger/noop.go

@@ -15,6 +15,7 @@ func (n noopLogger) InfoError(_ string, _ error)           {}
 func (n noopLogger) WarningError(_ string, _ error)        {}
 func (n noopLogger) DebugError(_ string, _ error)          {}
 
+// NewNoopLogger returns a logger which discards all events.
 func NewNoopLogger() mtglib.Logger {
 	return noopLogger{}
 }

logger/zerolog.go

@@ -114,6 +114,7 @@ func (z *zeroLogContext) attachCtx(evt *zerolog.Event) {
 	}
 }
 
+// NewZeroLogger returns a logger which is using rs/zerolog library.
 func NewZeroLogger(log zerolog.Logger) mtglib.Logger {
 	return &zeroLogContext{
 		log: &log,