[DOC] Fixed run command for the client still using Python instead of Go

README.md

@@ -63,7 +63,7 @@ or
 
 ```
 $ env KWKHTMLTOPDF_SERVER_URL=http://localhost:8080 \
-    client/python/kwkhtmltopdf_client.py https://wkhtmltopdf.org /tmp/test.pdf
+    go run client/go/kwkhtmltopdf_client.go https://wkhtmltopdf.org /tmp/test.pdf
 ```
 
 This should generate a printout of the wkhtmltopdf home page to /tmp/test.pdf.