E0201: Malformed attribute

An attribute is @ and a name, optionally with arguments (@doc("…"), @Route{Method: "GET"}). This one couldn't be read: no name after @, an unclosed ( or [, the wrong arguments for a built-in (@doc and @deprecated take one string, @export an identifier), or an attribute that isn't implemented.

Wrong

@doc(42)
func listUsers() []User { … }

Right

@doc("Lists the users")
func listUsers() []User { … }