chore: use early conn to support real ws 0-rtt

common/callback/callback.go

@@ -0,0 +1,25 @@
+package callback
+
+import (
+	C "github.com/Dreamacro/clash/constant"
+)
+
+type FirstWriteCallBackConn struct {
+	C.Conn
+	Callback func(error)
+	written  bool
+}
+
+func (c *FirstWriteCallBackConn) Write(b []byte) (n int, err error) {
+	defer func() {
+		if !c.written {
+			c.written = true
+			c.Callback(err)
+		}
+	}()
+	return c.Conn.Write(b)
+}
+
+func (c *FirstWriteCallBackConn) Upstream() any {
+	return c.Conn
+}