https://travis-ci.org/github/MarcoFalke/btc_nightly/jobs/680655419#L412
"A locked transaction output will not be chosen by automatic coin selection, when spending bitcoins.\n"
                "Locks are stored in memory only. Nodes start with zero locked outputs, and the locked output list\n"
                "is always cleared (by virtue of process exit) when a node stops or fails.\n"
                "Also see the listunspent call\n",
                {
                    {"unlock", RPCArg::Type::BOOL, RPCArg::Optional::NO, "Whether to unlock (true) or lock (false) the specified transactions"},
                    {"transactions", RPCArg::Type::ARR,  "empty array", "The transaction outputs and within each, the txid (string) vout (numeric).",
                        {
                            {"", RPCArg::Type::OBJ, RPCArg::Optional::OMITTED, "",
                                {
                                    {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The transaction id"},
                                    {"vout", RPCArg::Type::NUM, RPCArg::Optional::NO, "The output number"},
                                },
                            },
                        },
                    },
                },
                RPCResult{
                    RPCResult::Type::BOOL, "", "Whether the command was successful or not"
                },
                RPCExamples{
            "\nList the unspent transactions\n"
            + HelpExampleCli("listunspent", "") +
            "\nLock an unspent transaction\n"
            + HelpExampleCli("lockunspent", "false \"[{\\\"txid\\\":\\\"a08e6907dbbd3d809776dbfc5d82e371b764ed838b5655e72f463568df1aadf0\\\",\\\"vout\\\":1}]\"") +
            "\nList the locked transactions\n"
            + HelpExampleCli("listlockunspent", "") +
            "\nUnlock the transaction again\n"
            + HelpExampleCli("lockunspent", "true \"[{\\\"txid\\\":\\\"a08e6907dbbd3d809776dbfc5d82e371b764ed838b5655e72f463568df1aadf0\\\",\\\"vout\\\":1}]\"") +
            "\nAs a JSON-RPC call\n"