Fix errors caused by sync locks crossing `await` in `cli::authenticate`

src/helpers/cli.rs

@@ -7,6 +7,7 @@ use crate::{errors::Result, registration::Registered, Mastodon};
 pub async fn authenticate(registration: Registered) -> Result<Mastodon> {
     let url = registration.authorize_url()?;
 
+    let code = {
         let stdout = io::stdout();
         let stdin = io::stdin();
 
@@ -19,6 +20,25 @@ pub async fn authenticate(registration: Registered) -> Result<Mastodon> {
 
         let mut input = String::new();
         stdin.read_line(&mut input)?;
-    let code = input.trim();
+        input
+    };
+    let code = code.trim();
+
     registration.complete(code).await
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn send_sync() {
+        fn assert_send_sync(_: impl Send + Sync) {}
+
+        let mock_reg = || -> Registered { unimplemented!() };
+        let no_run = || async move {
+            let _ = authenticate(mock_reg()).await;
+        };
+        assert_send_sync(no_run());
+    }
+}