Hi @cheyuxuanll,
The correct syntax for consul kv get
is documented in the help output for the CLI command, and on the website at https://www.consul.io/commands/kv/get#usage.
$ consul kv get --help
Usage: consul kv get [options] [KEY_OR_PREFIX]
…
The options need to be specified before the key you are attempting to retrieve. In your particular scenario, the correct command syntax would be:
$ consul kv get -token=testtoken mysql
I hope this helps.