How to escape curly braces in a format string in Rust

You might be reading some out of date docs (e.g. for Rust 0.9)

As of Rust 1.0, the way to escape { and } is with another { or }

write!(f, "{{ hash:{}, subject: {} }}", self.hash, self.subject)

The literal characters { and } may be included in a string by
preceding them with the same character. For example, the { character
is escaped with {{ and the } character is escaped with }}.