set _X_AMZN_TRACE_ID environment variable for x-ray (#341)

Author: bnusunny

lambda-runtime/src/lib.rs

@@ -158,6 +158,9 @@ where
             trace!("{}", std::str::from_utf8(&body)?); // this may be very verbose
             let body = serde_json::from_slice(&body)?;
 
+            let xray_trace_id = &ctx.xray_trace_id.clone();
+            env::set_var("_X_AMZN_TRACE_ID", xray_trace_id);
+
             let request_id = &ctx.request_id.clone();
             let task = panic::catch_unwind(panic::AssertUnwindSafe(|| handler.call(body, ctx)));
 

lambda-runtime/src/types.rs

@@ -139,7 +139,7 @@ impl TryFrom<HeaderMap> for Context {
                 .to_owned(),
             xray_trace_id: headers
                 .get("lambda-runtime-trace-id")
-                .unwrap_or(&HeaderValue::from_static("No header lambda-runtime-trace-id found."))
+                .unwrap_or(&HeaderValue::from_static(""))
                 .to_str()?
                 .to_owned(),
             ..Default::default()