janriemer, "Can't move a closure into a spawned thread"
https://users.rust-lang.org/t/cant-move-a-closure-into-a-spawned-thread/111332
or phrased differently: "Misunderstandings of what the 'static lifetime in #Rust means".
Kornel's excellent answer:
https://users.rust-lang.org/t/cant-move-a-closure-into-a-spawned-thread/111332/8?u=janriemer"Note that any lifetime bounds, including 'static, apply only to references and types containing references. They do nothing when applied to self-contained types. This means that String is not 'static, but rather it isn't affected by any lifetime bound."