Update docs

ipblocklist/files/init.go

@@ -6,9 +6,16 @@ import (
 	"io"
 )
 
+// ErrBadHTTPClient is returned if given HTTP client is initialized
+// incorrectly.
 var ErrBadHTTPClient = errors.New("incorrect http client")
 
+// File is an abstraction for a entity that can be opened in some context.
 type File interface {
+	// Open returns an readable entity for a file. It is important to not forget
+	// to close it after the usage.
 	Open(context.Context) (io.ReadCloser, error)
+
+	// String returns a short text description for the file
 	String() string
 }