Email Forwarder: Pipe to program failed

I am trying out the pipe to program feature of the email forwarders. I began by making a little program in Rust. The program just created a text file at the same folder as the program itself is, and it wrote the parameters you give to it as an argument. I ran the program on my computer [CODE=bash]./my-program "argument"
. And it worked perfectly. (I also ran [CODE=bash]chmod 0700 my-program
as explained in the = env::args().collect(); let mut arg_str: String = String::new(); for arg in args { arg_str = format!("{} - {}", arg_str, arg) } let _firebase = firebase_rs::Firebase::new("https://email-test-76e8c-default-rtdb.europe-west1.firebasedatabase.app/").unwrap(); let users = _firebase.at("data").unwrap(); let _d1 = "{\"response\": \""; let _d2 = "\"}"; let d = format!("{}{}{}", _d1, arg_str, _d2); let res = users.set(&d).unwrap(); println!("{:?}", res); }