replace closure with auth_header function

I AM SO COOL

src/main.rs

@@ -9,13 +9,9 @@ mod client;
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
     let channel = Channel::from_static("dns:///youtube.googleapis.com:443").connect().await?;
-    let token: MetadataValue<_> = "Bearer my-secret-token".parse()?;
     let mut client = V3DataLiveChatMessageServiceClient::with_interceptor(
         channel,
-        move |mut req: Request<()>| {
-            req.metadata_mut().insert("authorization", token.clone());
-            Ok(req)
-        },
+		auth_header
     );
 
     let request = tonic::Request::new(LiveChatMessageListRequest {
@@ -36,7 +32,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
 
 async fn auth_header(mut req: Request<()>) -> Result<Request<()>, InvalidMetadataValue> {
 
-    let token: MetadataValue<_> = "Bearer my-secret-token".parse()?;
+    let token: MetadataValue<_> = "Bearer my-secret-token".parse().expect("failed to parse token");
 
 
 	req.metadata_mut().insert("x-goog-api-key", token).expect("WHAT");