Explicitly specify Send requirement where dyn traits are used (#296)

src/rust/api/client.rs

@@ -360,8 +360,8 @@ const BOUNDARY: &str = "MDuXWGyeE33QFXGchb2VFWc4Z7945d";
 /// to google APIs, and might not be a fully-featured implementation.
 #[derive(Default)]
 pub struct MultiPartReader<'a> {
-    raw_parts: Vec<(HeaderMap, &'a mut dyn Read)>,
-    current_part: Option<(Cursor<Vec<u8>>, &'a mut dyn Read)>,
+    raw_parts: Vec<(HeaderMap, &'a mut (dyn Read + Send))>,
+    current_part: Option<(Cursor<Vec<u8>>, &'a mut (dyn Read + Send))>,
     last_part_boundary: Option<Cursor<Vec<u8>>>,
 }
 
@@ -384,7 +384,7 @@ impl<'a> MultiPartReader<'a> {
     /// `mime`    - It will be put onto the content type
     pub fn add_part(
         &mut self,
-        reader: &'a mut dyn Read,
+        reader: &'a mut (dyn Read + Send),
         size: u64,
         mime_type: Mime,
     ) -> &mut MultiPartReader<'a> {