just exposing Go's html.UnescapeString
UnescapeString unescapes entities like "<" to become "<". It unescapes a larger range of entities than EscapeString escapes. For example, "á" unescapes to "á", as does "á" and "á". UnescapeString(EscapeString(s)) == s always holds, but the converse isn't always true.
install with
go install github.com/dgparker/unescape/cmd/unescape
run with
unescape "<entity1" "entity2á"