Most examples showing deserialization of JSON with Rust and serde_json show deserialization into a known structure format, using a defined struct.

I’m new to rust and decided to throw myself in the deep end. So I’m currently making a notes taking app in the terminal, and I want to save the notes in json format. But I keep getting this error:

I have some function, here called request, that returns a JSON string with some data. For example, an array with variable size. I can deserialize the JSON string into a Vec just fine with serde_json, but I have to call the request many times. I would like instead to reuse the Vec already created, instead of dropping and creating a new Vec every time deserialization happens.