The transaction signing process for the blockcypher ethereum API is explained here: https://www.blockcypher.com/dev/ethereum/#creating-transactions
When their "addrs" endpoint is called, their API creates a new ethereum address, and a 64-character private key is provided.
When their "/txs/new" endpoint is called, their API provides a "tosign" string which must be used with the 64-character private key, to produce a signature.
I need to know how to create that signature, which can be used with their "/txs/send" endpoint.
I do not wish to use their signer tool, because it requires that the GO programming language is installed on my server. If I get a new server, I don't want to have to reinstall a bunch of additional libraries.
I looked at the Bitwasp examples, and could not find a method that simply creates a transaction signature.
Please provide specific instructions which describe the simplest method to create a transaction signature for the blockcypher ethereum API.