Properly test for boolean "true"

"true" was treated as an invalid boolean. All strings in the slice of
valid boolean values need to be lowercase, since the input is lowercased
before comparison.

message.go

@@ -18,4 +18,4 @@ const (
 var False = []string{"off", "no", "0", "false"}
 
 // True is slice of array for true logical representation in string
-var True = []string{"on", "yes", "1", "True"}
+var True = []string{"on", "yes", "1", "true"}