added mutex to get contract details (#6)

Co-authored-by: Wil Boayue <wboayue@gmail.com>

Sync request channels (#5)

* sync channel access. stop stream on error
* cleanup

Fixes race condition (#3)

Wait for server to send next valid order id before sending requests.

Sending requests prior to this may cause the server to close the connection.

cleanup constants (#2)

Co-authored-by: Wil Boayue <wboayue@gmail.com>

cleanup

Cleanup message code (#1)

Converted message codes to go style and made them private

Cleanup message code (#1)

Converted message codes to go style and made them private

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