If dose not specify the 'ProtocolVersion' in 'mcp.InitializeParams', the MCP server will specify the low version during initialization phase. (#687)

For example, the mcp server dose support '2025-06-18' version. But if client dose not specify the version, the mcp server will use '2025-03-26'.
And, the other case is that the mcp client dose not need the latest '2025-11-25' version MCP features. But when client do initialization  with MCP server, the server select '2025-11-25' version during negotiation and raised "unsupported protocol version 2025-11-25" error. Since mcp-go library dose not implement the '2025-11-25' version mcp feature temporary.

fix issue #650.

Signed-off-by: hai.yue <hai.yue@ingka.com>

Author: yuehaii

client/client.go

@@ -213,6 +213,11 @@ func (c *Client) Initialize(
 		Capabilities:    capabilities,
 	}
 
+	// By default, use client supported lastest protocol version if version not specified
+	if params.ProtocolVersion == "" {
+		params.ProtocolVersion = mcp.LATEST_PROTOCOL_VERSION
+	}
+
 	response, err := c.sendRequest(ctx, "initialize", params, request.Header)
 	if err != nil {
 		return nil, err