feat(proto): add generic proto writer

proto/src/writer/protowriter.rs

@@ -0,0 +1,34 @@
+use async_trait::async_trait;
+use tokio::io::{AsyncWrite, AsyncWriteExt};
+
+pub struct ProtoWriter<W>
+where
+    W: AsyncWrite + Unpin + Send,
+{
+    pub(super) inner: W,
+}
+
+impl<W> ProtoWriter<W>
+where
+    W: AsyncWrite + Unpin + Send,
+{
+    pub fn new(writer: W) -> ProtoWriter<W> {
+        ProtoWriter { inner: writer }
+    }
+}
+
+#[async_trait]
+pub trait ProtoFlush {
+    async fn flush(&mut self) -> anyhow::Result<()>;
+}
+
+#[async_trait]
+impl<W> ProtoFlush for ProtoWriter<W>
+where
+    W: AsyncWrite + Unpin + Send,
+{
+    async fn flush(&mut self) -> anyhow::Result<()> {
+        self.inner.flush().await?;
+        Ok(())
+    }
+}