test: add function testing case

test/echo_server.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"fmt"
+
+	"frp/utils/conn"
+)
+
+var (
+	PORT int64 = 10701
+)
+
+func main() {
+	l, err := conn.Listen("0.0.0.0", PORT)
+	if err != nil {
+		fmt.Printf("echo server listen error: %v\n", err)
+		return
+	}
+
+	for {
+		c, err := l.Accept()
+		if err != nil {
+			fmt.Printf("echo server accept error: %v\n", err)
+			return
+		}
+
+		go echoWorker(c)
+	}
+}
+
+func echoWorker(c *conn.Conn) {
+	for {
+		buff, err := c.ReadLine()
+		if err != nil {
+			fmt.Printf("echo server read error: %v\n", err)
+			return
+		}
+
+		c.Write(buff)
+	}
+}