chore: set the default value for the options.protocol in the init() of options (#3387)

* chore: set the default value for the `options.protocol` in the `init()` of `options`

Signed-off-by: fukua95 <fukua95@gmail.com>

* add a test

Signed-off-by: fukua95 <fukua95@gmail.com>

---------

Signed-off-by: fukua95 <fukua95@gmail.com>

options.go

@@ -178,6 +178,9 @@ func (opt *Options) init() {
 			opt.Network = "tcp"
 		}
 	}
+	if opt.Protocol < 2 {
+		opt.Protocol = 3
+	}
 	if opt.DialTimeout == 0 {
 		opt.DialTimeout = 5 * time.Second
 	}

options_test.go

@@ -222,3 +222,26 @@ func TestReadTimeoutOptions(t *testing.T) {
 		}
 	}
 }
+
+func TestProtocolOptions(t *testing.T) {
+	testCasesMap := map[int]int{
+		0: 3,
+		1: 3,
+		2: 2,
+		3: 3,
+	}
+
+	o := &Options{}
+	o.init()
+	if o.Protocol != 3 {
+		t.Errorf("got %d instead of %d as protocol option", o.Protocol, 3)
+	}
+
+	for set, want := range testCasesMap {
+		o := &Options{Protocol: set}
+		o.init()
+		if o.Protocol != want {
+			t.Errorf("got %d instead of %d as protocol option", o.Protocol, want)
+		}
+	}
+}

redis.go

@@ -302,15 +302,9 @@ func (c *baseClient) initConn(ctx context.Context, cn *pool.Conn) error {
 	conn := newConn(c.opt, connPool)
 
 	var auth bool
-	protocol := c.opt.Protocol
-	// By default, use RESP3 in current version.
-	if protocol < 2 {
-		protocol = 3
-	}
-
 	// for redis-server versions that do not support the HELLO command,
 	// RESP2 will continue to be used.
-	if err = conn.Hello(ctx, protocol, username, password, c.opt.ClientName).Err(); err == nil {
+	if err = conn.Hello(ctx, c.opt.Protocol, username, password, c.opt.ClientName).Err(); err == nil {
 		auth = true
 	} else if !isRedisError(err) {
 		// When the server responds with the RESP protocol and the result is not a normal